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Virtual clinic: Applying technology to expand dentalschool walls

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Virtual clinic: Applying technology to expand dentalschool walls

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Dental hygienists are commonly affected by musculoskeletal disorders (MSDs) due to repetitive motions and awkward, static postures sustained during clinical practice. 1,2 Previous studies indicate 64% to 93% of dental hygienists have musculoskeletal pain or MSDs in the neck, back, shoulders, and wrists. ³⁻⁵ Additionally, research indicates MSDs may occur in student populations before their careers even begin. 6,7 Because of the high rate of MSDs and biomechanical risk factors dental hygienists experience, maintaining proper ergonomics is important to decrease the risk for work-related injuries and increase career longevity.

Ergonomics is the science of workplace design and job demands to increase efficiency and safety. 8,9 Ergonomics focuses on the nature of the work, armamentarium used, and the work environment. For dentistry and dental hygiene, this may include designing tools, equipment, work areas, and tasks to, ultimately, fit the nature of clinical practice to the clinician. ⁹ When applied, dental ergonomics may reduce the prevalence of MSDs in oral health professionals. 9,10 Research has examined equipment and practices and their effects on ergonomics. ¹¹⁻¹⁷ The following information may guide dental hygienists in making informed decisions about armamentarium choices and techniques to improve workplace safety. This may decrease their risk for MSDs and increase their knowledge of ergonomic practices and choices while providing dental hygiene care.

Ergonomic Considerations for Loupes

Adopting an ergonomically sound approach may reduce MSDs. Maintaining an upright sitting position with a neutral neck and trunk is recommended. 18,19 Loupes are often introduced in preclinical dental hygiene education and are promoted as an aid to neutral positioning. 7,11,12 The most popular type of loupes is through-the-lens (TTL) option in which the magnification ocular is mounted directly into the lens of the frame. Front-lens-mounted loupes have the oculars mounted to the frame rather than into the lens and are sometimes adjustable.

Some manufacturers are now offering loupes in which the ocular is positioned to allow clinicians to look forward without tilting their heads and necks downward to view the working area. While more research is needed, loupes of this type may allow dental hygienists to sit upright, adopt a neutral position, and reduce muscle strain on the neck. Overall, dental hygienists should consider loupes with adjustable vertical declination angle or those with steeper declination angles to maintain a neutral position for improved ergonomics.

Ocular Types and Magnification Considerations

The magnification power of loupes may offer ergonomic benefit, as it affects the working distance and field of view (area/​teeth and structures that can be viewed with clarity). 20,23,24 Loupes are generally classified into Galilean and Keplerian (prismatic). Galilean loupes use two lenses-one convex and one concave-and generally provide magnification between 2.0x and 3.5x. Keplerian loupes have two or more convex lenses with a prism offering higher magnification from 3.5x to 8x.

Dental hygienists should explore varying magnification strengths in a working position to find the best field of view and working distance to avoid compromising posture. The weight of different oculars on the frame or in the lens should also be considered as this may result in more forward tilting or muscle strain on the neck.

Lighting in Combination with Loupes

Insufficient lighting while performing dental hygiene tasks may lead to eye fatigue, unnecessary postural demands, and compromised performance. 3,29 Coaxial illumination (headlight) is often used with loupes and, while subjective, may help dental hygienists maintain a neutral posture. 23,30 Headlights are typically mounted directly to the frame of the loupes and align with the working area to provide a shadow-free environment and eliminate the need to adjust the overhead light. ²³

Alternative Seating Approaches to Improve Ergonomics

Prolonged seated hygiene work and assuming awkward postures while seated may also contribute to MSDs, particularly in the upper and lower back. ³³ Sitting in an upright position, with the spine in a natural "s" position with minimal forward flexion (< 20˚) reduces torque on the spine with gravity acting downward. 18,19 Lumbar lordosis (sitting upright while keeping the natural curvature of the lumbar spine) decreases spine pressure and ligament tension, and may reduce back pain. 34,35 Ergonomic chairs or saddle stools, especially when used with loupes and headlights, may facilitate a more balanced posture and alleviate poor postures. ³⁶

Conventional dental operatory chairs have a flat seat while ergonomic chairs or stools place the hips higher than the knees and the seat portion is tilted downward to open the hip angle and decrease pressure on the spine. ³⁷Ergonomic chair designs may have back support and/​or arm rests, and ergonomic stools typically resemble a saddle. Some studies have found improved posture with saddle stools and ergonomic chairs while performing dental-related tasks compared to conventional chairs. 14,36,38 Additionally, when used in combination with loupes, saddle stools may offer improved posture compared to traditional chairs without loupes. ³⁶

Postural variance throughout the workday may help reduce MSDs. Alternating between seated and standing positions may reduce time spent in static postures and may offer more variability for the muscles and joints. In various settings and jobs where seated postures are used, studies have examined postural variance (alternating seated and standing work) throughout the workday and have reported reduced musculoskeletal pain, reduced fatigue, and deceased spinal disorders. 39,40

Dental hygienists may see similar benefits when alternating seated and standing dentistry for sound ergonomic postures while working. A pilot study on dental hygiene students alternating seated and standing postures during dental hygiene work found no differences in posture as measured by Modified Dental Operator Posture Assessment Instrument compared to not alternating postures; however, all participants in the training group perceived their pain and posture were improved using an alternating seated/​standing protocol. ¹⁵ More research should examine proper standing postures and training in standing dentistry to effectively quantify if alternating between seated and standing postures improves ergonomics.

Instrument Selection and Considerations for Ergonomics

The fine, repetitive, and forceful movements dental hygienists perform while scaling and root planing may also contribute to MSDs, particularly in the wrist and forearms. 5,6 Periodontal instruments vary in their shape, weight, diameter, and material. Changing the weight and diameter of the instrument may influence muscle activity as well as pinch force.

Dong et al 16,41 in two separate studies found larger diameter (10 mm) instruments and lightweight instruments (15 g) required the least muscle load and pinch force during simulated scaling. Suedbeck et al ¹⁷ examined instrument handle design and forearm muscle activity using commercially available instruments and found the largest instrument (11.1 mm) with the heaviest weight (23 g) generated the most muscle activity. The weight of the instrument appeared to also be a significant factor in generating more muscle activity. Based on research, smaller instrument diameters seem to increase muscle activity and pinch force while scaling. Additionally, heavier instruments may cause more strain on the muscle and grip when scaling. 16,17,41

Conclusion

Due to the nature of clinical practice, dental hygienists are at an increased risk for MSDs which may cause pain, stress, and, ultimately, affect career longevity. Ergonomic education and making informed decisions on everything from equipment to posture are important to start early in the career to combat biomechanical risk factors. With the information above, dental hygiene students, practicing dental hygienists, and educators may be able to make more informed decisions related to the use of loupes, seating alternatives while working, and instrument selection while scaling to improve ergonomics related to dental hygiene practice.

References

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3. Morse T, Bruneau H, Dussetschleger J. Musculoskeletal disorders of the neck and shoulder in the dental professions. Work. 2010;35:419-429.

4. Akesson I, Johnsson B, Rylander L, Moritz U, Skerfving S. Musculoskeletal disorders among female dental personnel - clinical examination and a 5-year follow-up study of symptoms. Int Arch Occup Environ Health. 1999;72:395-403.

5. Anton D, Rosecrance J, Merlino L, Cook T. Prevalence of musculoskeletal symptoms and carpal tunnel syndrome among dental hygienists. AJ J Ind Med. 2002;42:248-257.

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7. Stambaugh JE, Calleros C, Siegel P, Nathe C. Evaluating the prevalence of musculoskeletal neck pain in dental hygiene students. J Dent Hyg. 2021;95:58-62.

8. Darby ML, Walsh MM. Dental Hygiene: Theory and Practice. 4th ed. St. Louis: Saunders; 2015:145-160.

9. Anu V, Suresh Babu AM, Madan Kumar KD. Insights about dental ergonomics among dental students: the need of the hour to recommend dental ergonomics in academic curriculum. J Adv Oral Res. 2018;949-954.

10. Shaik AR. Dental ergonomics: basic steps to enhance work efficiency. Arch Med Health Sci. 2015;3:138-144.

11. Hayes M, Osmotherly P, Taylor J, Smith D, Ho A. The effect of wearing loupes on upper extremity musculoskeletal disorders among dental hygienists. Int J Dent Hyg. 2014;12:174-179.

12. Carpentier M, Aubeux D, Armengol V, Pérez F, Prud'Homme T, Gaudin A. The effect of magnification loupes on spontaneous posture change of dental students during preclinical restorative training. J Dent Educ. 2019;83:407-415.

13. Ludwig EA, Tolle SL, Jenkins E, Russell D. Magnification loupes influence on neck and trunk flexion of dental hygienists while scaling-a pilot study. Int J Dent Hyg. 2021;19:106-113.

14. De Bruyne MA, Van Renterghem B, Baird A, Palmans T, Danneels L, Dolphens M. Influence of different stool types on muscle activity and lumbar posture among dentists during a simulated dental screening task. Appl Ergon. 2016;56:220-226.

15. Partido BB, Henderson R, Lally M. Impact of a seated-standing protocol on postures and pain among undergraduate dental hygiene students: a pilot study. J Dent Hyg. 2021;95:70-78.

16. Dong H, Loomer P, Barr A, et al. The effect of tool handle shape on hand muscle load and pinch force in a simulated dental scaling task. Appl Ergon. 2006;38:525-531.

17. Suedbeck JR, Tolle SL, McCombs G, Walker ML, Russell DM. Effects of instrument handle design on dental hygienists' forearm muscle activity during scaling. J Dent Hyg. 2017;91:47-54.

18. Haughie LJ, Fiebert IM, Roach KE. Relationship of forward head posture and cervical backward bending to neck pain. J Man Manip Ther. 1995;3:91-97.

19. Gherig J, Sroda R, Sacuzzo D. Fundamentals of Periodontal Instrumentation and Advanced Root Instrumentation. 8th ed. Baltimore: Lippincott Williams & Wilkins; 2017.

20. Rucker LM, Beattie C, McGregor C, Sunell S, Ito Y. Declination angle and its role in selecting surgical telescopes. J Am Dent Assoc. 1999;130:1096-1100.

21. Chang BJ. Ergonomic benefits of surgical telescope systems: selection guidelines. J Calif Dent Assoc. 2002;30:161-169.

22. Wilson C, Johnson T, Seiger C. Dental magnification loupes and head tilt angles among aental hygiene students and faculty: a comparative study. J Dent Hyg. 2021;95:59-64.

23. Chang BJ. Guidelines for selecting economically correct surgical telescope systems. Dental Economics. 2003;93(11):84-91.

24. Syme SE, Fried JL, Strassler HE. Enhanced visualization using magnification systems. J Dent Hyg. 1997;71:202-206.

25. Aldosari MA. Dental magnification loupes: an update of the evidence. J Contemp Dent Pract. 2021;22:310-315.

26. Perrin P, Eichenberger M, Neuhaus KW, Lussi A. Visual acuity and magnification devices in dentistry. Swiss Dent J. 2016;126:222-235.

27. Urlic I, Verzak Z, Vranic D. Measuring the influence of galilean loupe system on near visual acuity of dentists under simulated clinical conditions. Acta Stomatologica Croatica. 2016;50:235-241.

28. Mamoun JS. A rationale for the use of high-powered magnification or microscopes in general dentistry. Gen Dent. 2009;57:18-26.

29. Dianat I, Sedghi A, Bagherzade J, Jafarabadi MA, Stedmon AW. Objective and subjective assessments of lighting in a hospital setting: implications for health, safety and performance. Ergonomics. 2013;56:1535-1345.

30. Bly J, Jordre B. Improve visibility. Dimensionss of Dental Hygiene. 2015;13:18-23.

31. Arnett M, Gwozdek A, Ahmed S, Beaubien H, Yaw K, Eagle I. Assessing the use of loupes and lights in dental hygiene educational programs. J Dent Hyg. 2017;91:15-20.

32. Kissell D, Partido B, Moore W. Magnification and coaxial illumination in dental hygiene education: experience and attitudes of clinical educators. J Dent Hyg. 2019;93:7-15.

33. Leggat PA, Kedjarune U, Smith DR. Occupational health problems in modern dentistry: a review. Ind Health. 2007;45:611-621.

34. Pynt J, Higgs J, Mackey M. Seeking the optimal posture of the seated lumbar spine. Physiother Theor Pract. 2001;17:5-21.

35. Hedman TP, Fernie GR. Mechanical response of the lumbar spine to seated postural loads. Spine. 1997;22:734-743.

36. Dable RA, Pradnya WB, Babita YJ, Smita MI, Ashishkumar PK, Sunilkumar NN. Postural assessment of students evaluating the need of ergonomic seat and magnification in dentistry. J Indian Prosthodont Soc. 2014;14:51-58.

37. Harrison DD, Harrison SO, Croft AC, et al. Sitting biomechanics part 1: review of the literature. J Manipulative Physiol Ther. 1999;22:9:594-609.

38. Gandavadi A. Working postures in dental practitioners and dental students: relationships between posture, seating, and muscle activity. Available at: etheses.bham.ac./​k/​id/​eprint/⯐/䁯/​Gandavadi08PhD.pdf. Accessed August 17, 2022.

39. Grobler SH, Mostert K, Becker P. The impact of a change in work posture from seated to stand-up on work-related musculoskeletal disorders among sewing-machine operators. Am J Ind Med. 2018;61:699-711.

40. Hasegawa T, Inoue K, Tsutsue O, Kumashiro M. Effects of a sit-stand schedule on a light repetitive task. International Journal of Industrial Ergonomics. 2001;28(3-4):219-224.

41. Dong H, Barr A, Loomer P, et al. The effects of periodontal instrument handle design on hand muscle load and pinch force. J Am Dent Assoc. 2006;137:1123-1130.

42. Suedbeck JR, Armitano-Lago C. The effects of the traditional scaling technique versus a modified scaling technique on muscle activity and pinch force generation: a pilot study. J Dent Hyg. 2021;95:6-13.

From Dimensions of Dental Hygiene. September 2022; 20(9)14,16,18,21.

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Ergonomic Equipment Considerations for the Dental Hygienist - Dimensions of Dental Hygiene | Magazine

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Dimensions of Dental Hygiene is a monthly, peer-reviewed journal that reconnects practicing dental hygienists with the nation's leading educators and researchers. Dimensions is committed to the highest standards of professionalism, accuracy, and integrity in our mission of education supporting oral health professionals and those allied with the dental industry.

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The Relationship Between Surgical Loupes Usage, Workplace Ergonomics, and Musculoskeletal Disorders Among Saudi Ophthalmologists

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Evaluation of the ergonomic sitting positionadopted by dental students while usingdental simulators

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Evaluation of the ergonomic sitting positionadopted by dental students while usingdental simulators

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Musculoskeletal disorders related to dental hygienist profession

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Musculoskeletal disorders related to dental hygienist profession

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Prosthodontics Department, Faculty of Dentistry, Jordan University of Science and Technology, Irbid 22110, Jordan

Department of Managing Health Services and Hospitals, Faculty of Business Rabigh, College of Business (COB), King Abdulaziz University, Jeddah 21991, Saudi Arabia

Department of Health Services and Hospital Administration, Faculty of Economics and Administration, King Abdulaziz University, Jeddah 21589, Saudi Arabia

College of Dentistry, Jordan University of Science and Technology, Irbid 22110, Jordan

Author to whom correspondence should be addressed.

1. Introduction

Dental staff spend their workdays in stiff, inflexible positions, carrying out procedures with high precision and focus in a very narrow, enclosed space, the patient's mouth. Because the profession requires steady hands, strained stances, and static work, occasional pain in staff's neck, shoulder, and back areas is expected. Those rather seemingly not harmful working positions are repeated so often that they eventually may result in injuries [ 6].

Occupational risk factors that contribute to MSDs include deviated working postures, repetitive motion, forceful exertions, exposure to vibrating tools, prolonged work duration, mechanical stress, poorly designed dental equipment, and other factors [ 7]. MSDs are considered a multifactorial problem, which explains why the effect of a single ergonomic intervention is limited [ 8].

MSD symptoms include difficulty performing routine movements, motion limitation, tingling numbness, twitchy movements, weak grip, fatigue, pain, cramps, stiffness, and tenderness of affected body parts [ 9]. MSDs can be mild and infrequent but can be severe, chronic, and debilitating [ 10].

Established MSDs lead to difficulty in task performance, absenteeism, reduced productivity, decreased job satisfaction, financial losses from lower working hours, medical expenditure for therapy, and early retirement by dental professionals [ 8].

This project aims to directly inform dental personnel within the workplace and enable them to evaluate their practices regarding ergonomics. This knowledge transfer helped staff identify occupational MSD hazards and how to make workplace changes based on evidence-based ergonomics health promotion recommendations. It highlights how the change management theory of John Kotter, expressed in his 8-step model, could help dental personnel make the transition to better and smarter ways of working ergonomically and ultimately reducing the risks associated with MSDs. Staff were encouraged to engage in the project that aimed to reduce and prevent MSDs and build up a maintainable, ergonomic dental culture. Dental ergonomics literature is a wide topic area and has been the subject of numerous documented studies worldwide [ 1, 4, 8, 11, 16, 17]. The Kotter model has been used as an implementation guide to lead change efforts in various educational and healthcare settings [ 18, 19, 20, 21, 22]. This action research paper contributes to the literature by choosing the Kotter model as a framework to empower individuals and organisations to implement an ergonomic initiative to tackle MSDs.

2. Materials and Methods

2.1. Embracing Ergonomic Interventions

A 30-chair dental facility that provides services to the community is currently undergoing organisational change to implement an ergonomics intervention program. The dental centre employs 45 dental personnel, many of whom experience MSDs. Implications were not just limited to regular sick leave, but also included reduced productivity, and decreased working hours. Staff members who had MSDs needed various treatment modalities, ranging from over-the-counter pain medications, physiotherapy sessions, and splinting to even surgery, such as carpal tunnel surgery. The staff members acknowledge that inadequate control of MSDs and the means of their prevention should be addressed. Effective measures to avoid MSDs should be accepted as a norm and a routine standard by dental health workers.

This action plan project applies Kotter's eight-step change model to implement ergonomic prevention strategies to develop a workplace culture free of MSDs. The project's dual goals are to reduce and prevent MSDs and to enhance a dental ergonomic mindset. John Kotter's change management model was adopted because it is a simple progressive model that emphasises adapting to change, and the transition between its stages is easier [ 18]. It is a highly adaptable framework for a health care setting [ 19]. Key ergonomic interventions and their relevant effects will be based on the most current state of literature review research on ergonomic interventions [ 8]. Each phase in Kotter's change model will be linked with examples from ergonomic interventions, considering the limitations and shortcomings. The ultimate purpose is to gradually bring the best ergonomics improvement ideas into the dental practice to reduce MSDs by applying the Kotter change model.

Kotter studied the change efforts of more than 100 organisations before formulating his model for successful change. He proposed eight stages to produce a successful change in organisations [ 20]. The eight steps are grouped into three distinct phases ( Table 1). The process focuses on the "see-feel-change" approach by relating to peoples' emotions to successfully change their behaviours [ 21].

There was a six-month interval allocated for this project. A Gantt chart was helpful to keep track of the project timeline and the progress intended.

We thoroughly reviewed dental ergonomic interventions that aim to reduce or prevent MSDs. A research action plan design was created to implement such interventions in a dental setting, using the phases in the Kotter model. Action research is a reflective process of ongoing problem solving by a researcher who collaborates with others in a team to improve how they address issues in their organisation [ 22]. Carrying out a research action project provides a methodology with effective cycles of planning, acting, evaluating, and reflecting, ultimately generating knowledge and experience that will shape the future direction of further research [ 23]. Action research uses knowledge from problem-solving in reality [ 24, 25]. This research article integrated a qualitative case study methodology to depict the ergonomic change process that took place. An interventional case study design can help show how a planned organisational initiative advances [ 26]. Our hypothetical assumption is that adopting Kotter's change management model will be constructive in the ergonomic change effort. The ergonomic initiative applied Kotter's 8 steps, which are as follows: establish a sense of urgency, form a powerful guiding coalition, create a strategic vision, communicate the vision, empower others to act on the vision, create short-term wins, consolidate improvements, and institutionalise new approaches.

This study took place in a 30-chair dental facility, with 45 dental and allied dental staff representing our study's sample. Two of the authors were part of the five -member ergonomic team that led this initiative and selected various tools and strategies to improve the status quo dental ergonomics. Their duties ranged from allocating educational resources, creating brochures, arranging training sessions, applying fishbone analysis, tracking the 6-month project by a Gantt chart, and evaluating the ergonomic change. The following two methods were used to appraise the outcomes or the impact of Kotter's change model:

(i)

A 12-item checklist was developed in the project's first phase, based on evidence-based ergonomic interventions mentioned in the literature review [ 11]. The preliminary data from the checklists will serve as baseline information for capturing the ergonomic compliance witnessed. The participants responded to each item on the checklist with simple "yes/no" responses. The checklist is shown in Table 2.

(ii)

Comparing the number of sickness absence rates due to MSDs before and after implementing the ergonomic change was another evaluation method. Sick leave data were obtained from electronic medical records, and a prospective drop in sick leave rates due to MSDs was considered an ergonomic improvement [ 16].

2.1.1. Step 1. Create a Sense of Urgency

A creator of urgency for the ergonomic change could be affirming the numbers of staff with MSDs in the institution. This will prompt the dental staff to start open discussions about MSDs and how to take actions and consider techniques to work ergonomically. The staff's deposition or testimonial about the course and impact of a musculoskeletal problem and sharing their personal stories is a powerful option to create such a sense of importance. MSDs result in reduced work performance, reduction in routine activities, pain that prevents staff from going to work, and early retirement. Taking analgesics, physiotherapy, and even surgical interventions may be needed to overcome this affliction. Each dental health worker must understand the physical demands of the practice.

A more interactive approach would be arranging a visit by an occupational therapist or a dental ergonomics expert to the dental institution. A convincing dialogue with management about empirical ways to reduce and prevent MSDs would result in financial benefits, increased productivity, and better quality of work. High staff turnover because of MSDs is detrimental because skilled dental personnel may be difficult to replace. A combination of staff's MSD complaints, MSD-related sick leave, managerial involvement, open communication among colleagues, and an ergonomist's invitation creates a catalyst for urgency.

2.1.2. Step 2. Build an Ergonomic Coalition

An essential step to promote ergonomics in the dental organisation is to obtain management commitment and sponsorshiManagement must participate in goal setting and resource allocation in any ergonomic process and be a part of the ergonomic team. The guiding coalition or team comprises key staff representatives interested in deploying ergonomics. The five-member team included a consultant dentist, a clinician, a dental assistant, a hygienist, and a dental procurement manager. Team members represented a good mix from different levels and possessed distinct skill attributes. Among these attributes were familiarity with ergonomic knowledge, leadership roles, enough stature, credibility and official authority [ 27, 28]. Other qualities needed included persuasiveness to talk the staff into protecting themselves against MSDs, confidence in finding solutions, thoroughness in probing staff's doubts, and imaginative communication using various channels [ 29, 30]. Perhaps more important for the ergonomic task force is to have an "analysis-think-change" mindset by leading, encouraging and motivating colleagues to achieve the vision of sound ergonomic practices [ 21]. The team played a key role in driving ergonomic plans, communicating them to staff and enabling or gradually procuring ergonomic resources.

2.1.3. Step 3. Form the Ergonomic Vision

The vision is to build an ergonomics-sensitive culture within the dental workplace to prevent MSDs. Kotter stated that it is likely to be too inaccessible if the vision cannot be communicated in five minutes or less. A good vision statement can be made clear in a "sixty-second elevator ride" [ 31]. Any desired ergonomic change should entail a future vision for a working environment with avoidable MSDs. The project should begin with a clear vision of the presumed change and proceed with actions to make this change happen [ 32]. Meetings, ergonomic educational sessions, and conversations with staff are key moments that can be used to highlight a sense of urgency, encourage staff to buy in, build a guiding team and create better practical ergonomics [ 20]. These three steps help initiate an ergonomic climate.

2.1.4. Step 4. Communicate the Vision and the Initiatives

Actions and strategic initiatives need to be taken to achieve the ergonomic vision [ 20]. The task force formulated the following plan that must be executed:

Develop a user-friendly information brochure entitled "MSDs Prevention among Dental Personnel". (See Appendix A).

Identify available educational resources and construct training materials, such as videos, posters, and lectures.

Take advantage of periodic staff meetings and education sessions, such as the dental journal club, to identify ergonomic behaviours.

Design a fishbone diagram to help dental personnel understand the causes of musculoskeletal problems. (See Figure 1).

Review various strategies or recommendations advocated to reduce ergonomic problems.

Conduct research on ergonomic dental equipment to assist in the funding decisions required. Managers have a crucial role in supporting and enabling the adoption of ergonomic technologies.

Look to others who have led similar ergonomic projects. For instance, the team reviewed a comparable ergonomic program proposed by the Occupational Safety and Health Administration (OSHA). The program included the following six elements: management leadership, hazard information and reporting, job hazard analysis and control, ergonomic awareness training, MSD management, and program evaluation [ 24].

Encourage and involve others to suggest and discuss ergonomic improvement ideas.

Create a Gantt chart to monitor project progress and document ergonomic progress and obstacles.

These coordinated initiatives can turn the ergonomic vision into a reality.

2.1.5. Step 5. Empower Staff to Act on the Vision and Remove Obstacles

Staff were empowered to adapt ergonomic interventions. The ergonomic team that endorsed the project provided knowledge concerning how these interventions mitigate MSDs, what staff training is needed, and the ergonomic expenses. The literature review presented different ergonomic interventions. Ergonomic dental chairs, magnification loupes, prismatic spectacles, dental instruments, and educational training sessions in ergonomics had a significant positive impact on MSDs [ 8]. Ergonomic dental chairs, such as the saddle stool and dental chairs with arm support, provided comfort, maintained the natural curvature of the lower back, and improved the working posture [ 33, 34]. The use of magnification loupes improved the working posture and significantly reduced symptoms of MSDs [ 35, 36]. Prismatic spectacles significantly and positively changed the working posture, reduced MSD complaints, and simplified daily dental work [ 37, 38]. Proper selection of lightweight dental instruments with a wide diameter, rather than heavyweight instruments with a narrow diameter, significantly lowered MSD symptoms [ 39]. Hard-wearing automated hand tools should be incorporated instead of manual ones [ 40]. Theoretical and practical educational training courses in ergonomics included in-person coaching, circulating pamphlets, evaluating workstation conditions, modifying working postures, taking periodic micro-breaks, and explaining chair side stretching movements and strengthening exercises by a physiotherapist or an occupational therapist. Research-based knowledge gained through such training programs reduced the prevalence of MSDs and improved workplace ergonomics [ 41, 42, 43]. Other considerations to "ergonomize" the dental office include practising four-handed dentistry, appropriate lighting, indirect mirror viewing, good temperature and ventilation, alternating between sitting and standing, scheduling appointments to interchange between easy and difficult cases, selecting patient chairs with cervical rests, cordless handpieces, and voice-activated charting [ 40, 44, 45, 46, 47, 48, 49, 50]. Acquiring advances such as intuitive extraction kits, spinning self-cleaning dental mirrors, dry field illuminators, personal LED headlights, laser, Cad-Cam technology, ergonomic gloves, and other innovations indicate the wide scope and continuous evolution of dental ergonomics [ 51, 52, 53, 54]. New ergonomic skills will change custom practices, and staff need to familiarise themselves with such skills in the workplace.

2.1.6. Step 6. Create Quick Ergonomic Wins

Kotter suggested that short-term wins energised the project and reinforced momentum for success [ 55]. Successfully deploying early and easy ergonomic improvements is important before choosing to implement costly dental delivery systems. For example, short-term wins may include attending ergonomic training sessions, choosing alternate instrument grips, improving body posture, chair side stretching, sequencing treatment schedules, wearing loupes, and reducing MSDs. Achieving short-term wins enlightens the sceptics, engages staff, reveals benefits, and helps evaluate the progress of the process [ 32]. Any evidence that demonstrates ergonomic progress must be made clear and visible to all staff to build on the correct ergonomic practices and improve them. Such positive ergonomic results were delivered to staff by the guiding team in official meetings, coaching sessions, and casual conversations.

2.1.7. Step 7. Build on the Ergonomic Change

Organisational change could be a slow process and may take considerable time to maintain [ 21]. Slowly implementing ergonomic changes into the practice is necessary, and these short-term wins are only the beginning of what needs to be achieved in the long term [ 31, 32]. Any change process represents a continuous improvement cycle. Similarly, ergonomic change in the dental setting has no ultimate end. There are always new ergonomic approaches to consider and seek.

2.1.8. Step 8. Anchor the Ergonomic Culture

When operating ergonomically becomes the norm within the core of the dental setting, it could be said that the change was implemented. Consolidating the ergonomic change requires recognising and rewarding the behaviours of all staff involved in the process. Harvesting the fruits of working comfortably, experiencing better productivity, and preventing and reducing MSDs will help sustain the change in practice.

3. Project Outcomes and Discussion

This section provides a concise and precise description of the experimental results, their interpretation, and the experimental conclusions that can be drawn.

The project was evaluated using two assessment tools. Data were collected using checklists to measure ergonomic improvements in dental office practice status. The ergonomic team collected the data. The checklist acts as an initial assessment of ergonomic improvement post-implementation at the workplace after in-service education of MSD hazards, and ergonomic awareness has been carried out. An important opportunity to invest in is exercising caution in purchasing ergonomic dental equipment, and such a measurement is tangible and specific. Another evaluation tool used in the project was reducing MSD complaints and their sick leave or absence levels. Other suggestive screening tools utilised in ergonomic programs may include walk-through observational surveys of dental facilities, interviews with dental professionals, and assessments by surveys. However, these measurements were not evaluated within the limits of the time framework of the project.

When collecting data using checklists, the guiding team received positive comments from staff who expressed good awareness and interest in incorporating sound ergonomic principles into their daily practice. Conducting these ergonomic assessment checkpoints helps reveal sources of ergonomic risks and identify areas for improvement. The checklist results are shown in Table 3 and illustrated by a bar chart in Figure 2.

Eighteen dental staff members (41%) performed chair-side stretching, an intervention that can be easily carried out. Periodic stretching stimulates blood circulation, increases the production of synovial fluid in joints to keep them moving smoothly, releases aching trigger points, and helps muscles to achieve a productive range of motion [ 61].

The results of the checkpoints also show that less ergonomic sophistication was apparent, given that there was low employment of surgical loupes and less notable newly purchased ergonomic equipment. Only ten dental personnel (22%) used magnification loupes. Staff may resist using magnification loupes for several reasons. The considerable price of loupes and their longer learning curve may partly explain this finding [ 62]. It is important to use dental loupes as they improve posture, increase visual acuity and reduce MSDs [ 63, 64]. The financial barrier against using loupes could be removed if management assists staff with financing by deducting some of their employees' wages over a year to cover the costs of loupes, paying for a share of the loupes, or agreeing that the loupes could be claimed by the employee after one or two years [ 65].

Within the project's timeline, seven sorts of newly purchased dental products had noteworthy ergonomic features. It makes sense as management carries thorough research before investing in new ergonomic equipment [ 66]. These products included double-sided, magnified mirrors, padded periodontal instruments with thick silicone handles, cordless prophylaxis handpieces, high-speed handpieces with fibre-optic options, self-aspirating dental cartridge syringes for analgesia, ergonomic gloves, and a recently developed rubber dam system.

Double-sided mirrors achieve tissue retraction and indirect vision together [ 67]. Using instruments with a thick diameter (12-14 mm) silicon handles causes lower musculoskeletal strain [ 68]. Cordless prophy handpieces with a thick diameter, a tactile grip and light weight with essentially no cord pullback helped reduce workload and fatigue [ 48]. Fibre-optic equipped handpieces optimise light on the dental site, resulting in less strain for dental staff [ 69]. Ergonomic self-aspirating syringes are efficient compared to poorly controlled, conventional syringes during aspiration [ 70]. Light pliant gloves that fit snugly and do not apply pressure on the hands provide comfort [ 44, 71]. Modern rubber dam isolation systems exhibit quicker handling time and more effective isolation than conventional systems [ 72].

The majority of staff, 40 (88%), reported practising four-handed dentistry whenever applicable. Four-handed dentistry helps deliver dental care ergonomically and efficiently [ 77]. Four-handed dentistry is a teamwork approach, where dental staff work together in an ergonomically planned manner to improve efficacy, quality of care, and comfort [ 78] This proper layout promotes ergonomics and focuses on efficiently swapping tools between the operator and the dental assistant [ 79].

Concerns about adopting ergonomic posture in clinics were still perceptible and mainly attributed to efforts to change old working habits and work slowly. Thirty staff members (66%) reported attaining an ergonomic posture during work. The ergonomic or balanced, recommended posture features the oral health professional sitting as close as possible to the patient with their head inclined slightly forward, an upright torso, horizontal shoulders (not raised), arms close to the body, and both feet supported flat on the floor, and with thighs parallel to the ground, forming 90° with the legs [ 80, 81, 82].

The ergonomic project revealed clinics that had inadequate workspace or poor lighting. These clearly represented ergonomic strain. Staff complained of one clinic with a cramped workspace. Inadequate workspace will cause needless movement of staff, delay in completion of appointments, and an unfavourable psychological effect on staff [ 83]. Two other clinics presented with poor lighting. Poor lighting exposes dental staff to eye fatigue, headache, weariness, and psychological stress [ 84]. Both of these situations were resolved.

Ten out of sixty operator stools warranted repair or replacement. Ergonomic dental stools should be adjustable and provide lumbar support and armrests [ 85]. Specialised saddle stools are also considered ergonomic, offering a convenient natural lower back curve and a correct shoulder neck posture [ 33].

The percentage of staff that alternated between sitting and standing posture was 88% (n = 40). It was found that combining the sitting and standing working postures reduces fatigue and discomfort [ 86]. Standing minimises pressure on the back, and sitting transfers weight to the seat; hence, alternating between postures allows muscle workload to move from one body area to another [ 87].

Fifteen out of thirty patients' dental chairs had no adjustable headrests. Adjustable headrests support effortless access for the dental operator, and multi-articulated headrests improve viewing by positioning patients' heads along three axes [ 88].

Newly purchased dental tools that had lighter weights and larger diameters within the project's timeline were periodontal scalers and curettes. The research supports the belief that lighter and wider instruments produce less pinch force and muscle load, i.e., better ergonomics [ 60, 89].

The budget factor for the management may limit the incorporation of more costly ergonomic equipment and expensive hands-on training sessions. However, the dental staff may consider purchasing personal equipment, namely, magnification systems for themselves. Besides the quality, infection control, and journal club teams present in the centre, the ergonomic team laid the basis for further development in the future.

The notion that "in order to be a dentist, there must be an inevitable ergonomic compromise" should change. One interesting perspective from a dental teammate was as follows: "I know I have to practice ergonomically more often to lessen fatigue incidents. But when will this ergonomic practice become habitual?" Practice is the key. In Kotter's words," let it stick!".

4. Conclusions

MSDs are frequently reported by dental personnel, given the occupational risk factors. They may involve the lower back, hands, shoulders, or neck. They are cumulative and may build over the years. However, they can be avoided by practices and behaviours that are considered ergonomic. This action plan study sought to employ Kotter's structured eight-step framework for adopting an ergonomic workplace culture to prevent the likelihood MSDs. Kotter's model can help clarify and craft the new ergonomic practices by seizing opportunities and addressing challenges. Kotter's model, expressed in his eight-step process (developing urgency, building a guiding team, creating a vision, encouraging staff to buy-in, enabling action, creating short-term wins, encouraging consistency and permanent behaviours) represented a working framework to guide ergonomic recommendations and practice changes for dental staff. Promising outcomes of the change process were achieved, including the release of an informational brochure, a 2% reduction in MSD-related sickness absence rate, and ergonomic awareness, behaviours, and practice improvements.

4.1. Research Limitations/Implications

This project was implemented in a dental workplace within six months. Changes in the ergonomic status of practice were measured using MSD-related absence levels and checklists. These could be considered "short-term" wins, as Kotter implied. However, different evaluation instruments, such as surveys, interviews and observational tools, could be used. Many factors, such as general health, number of patients treated per day, and detailed work positions, were not considered. More time and resources may be needed to analyse these factors. Dental ergonomics has a wide scope indeed. Costly ergonomic equipment or resources and being unable to change old working behaviours or habits could also be limiting factors. However, there is great potential for simpler ergonomics.

4.2. Practical Implications

A change management model could be indicative when considering ergonomic practice changes in the dental workplace. Kotter's change model was chosen for this study. The steps within the model aid us in enabling ergonomic practice change and overcoming any barriers to such a practice. Ergonomic knowledge and interventions are critical to enable change to happen. Future ergonomic plans that may be proposed may include learning web-based portals, online websites, and hands-on training. The ergonomic process is continual because there is always room for improvement with various tools of evaluation.

Author Contributions

Conceptualization, R.J.A. and A.T.A.; methodology, A.A.; software, F.N.A.; validation, R.J.A., A.A. and A.T.A.; formal analysis, A.A. and F.N.A.; investigation, R.J.A. and A.T.A.; resources, F.N.A.; data curation, R.J.A. and A.T.A.; writing-original draft preparation, R.J.A.; writing-review and editing, R.J.A., A.T.A. and A.A.; visualization, F.N.A.; supervision, R.J.A. and A.A.; project administration, R.J.A. and A.A.; funding acquisition, F.N.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Informed Consent Statement

In the introduction part of the checklist, a consent form was added, including information about the researchers and research institution, research purpose, duration to complete the checklist, contact information, and a statement that the agreement is voluntary as below: I have read and understand the provided information and have had the opportunity to ask questions. I understand that my participation is voluntary and that I am free to withdraw at any time, without giving a reason and without cost.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

Appendix A

Figure A1. Informational brochure identifying work-related MSDs among dental personnel, their risk factors and evidence-based preventive ergonomic approaches.

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Anshasi RJ, Alsyouf A, Alhazmi FN, AbuZaitoun AT. A Change Management Approach to Promoting and Endorsing Ergonomics within a Dental Setting. International Journal of Environmental Research and Public Health. 2022; 19(20):13193. https://doi.org/10.3390/ijerph192013193

Chicago/Turabian Style

Anshasi, Rami J., Adi Alsyouf, Fahad Nasser Alhazmi, and Abeer Taha AbuZaitoun. 2022. "A Change Management Approach to Promoting and Endorsing Ergonomics within a Dental Setting" International Journal of Environmental Research and Public Health 19, no. 20: 13193. https://doi.org/10.3390/ijerph192013193

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A Change Management Approach to Promoting and Endorsing Ergonomics within a Dental Setting

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Musculoskeletal pain and disorders (MSDs) constitute a well-recognised occupational hazard to the dental community. Fortunately, they are preventable. Dental office ergonomics plays a key role in addressing these musculoskeletal challenges. An ergonomic improvement project based on Kotter’s eight-step change model management theory was implemented within a dental practice.

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Academic Editors: Daniela Ohlendorf and Nicola Magnavita

Received: 9 September 2021 / Revised: 18 October 2021 / Accepted: 20 October 2021 / Published: 26 October 2021

Studies demonstrate that there is a lack of effective ergonomic principles for adopting a neutral posture during the execution of dental procedures. ISO 11.226:2000 Standard, Corr. 1:2006 has been thoroughly evaluated and adapted to the way that dentists work by the European Society of Dental Ergonomics (ESDE). However, after 15 years, no studies that showed strong evidence of effectiveness in reducing the prevalence of awkward posture in applying its parameters within the scope of dental practice were found. The aim of this study was to verify the effectiveness of applying the ergonomic parameters proposed by the European Society of Dental Ergonomics (ESDE) and ISO 11226 in reducing the prevalence of the main awkward postures adopted by female dental surgeons during the execution of dental scaling on a dental mannequin. A randomized clinical trial was carried out with sixty dental surgeons randomly assigned to two groups: the intervention group, who received instructions and theoretical and practical ergonomic training; and the control group, who received the same training only at the end of the study. For data analysis, Software IBM SPSS 27 and RStudio was used. Descriptive statistics were performed to verify the effectiveness of the intervention, and generalized linear models (specifically, generalized estimated equation models) were used. Poisson distribution was carried out with log link function and network analyses. Sixty female dental surgeons participated in the study. Twenty-two were distributed in the intervention group and thirty-eight in the control group. It was found that ergonomic training enabled a 63% reduction in the prevalence of awkward postures and that there was a statistically significant difference (p < 0.001) only in the intervention group. The analyses showed that the estimated marginal means of postures not recommended in the groups' initial control, final control, initial intervention, and final intervention were 8.6, 8.2, 9.0, and 3.4, respectively. The relationship of networks analyses of the variables is shown with different profiles in the control and intervention groups, but the same pattern between the groups only vary in the strength and direction of the correlations. It was concluded that the ergonomic training based on the parameters of ISO 11226 and DIN EN 1005-4, and its adaptations to the dental practice provided by the European Society of Dental Ergonomics, as well as recent studies, contributed significantly to reducing the prevalence of awkward postures adopted by female dentists during the simulation of the basic periodontal procedures; however, it was not effective enough to improve the posture of the head and neck.

1. Introduction

Knowledge about ergonomics has advanced a lot. Studies have revealed its importance for the quality of life of the dentist. However, there is a great lack of application of its concepts and principles in dental practice [ 1, 2, 3, 4, 5, 6]. Scientific evidence indicates the high prevalence of joint, muscle, lumbar problems, and other work-related musculoskeletal disorders (WMSD), mainly due to poor posture, lack of ergonomic planning of equipment, work environment, work systems, among others [ 2, 7, 8, 9, 10, 11, 12, 13]. This has caused many dentists to work with low productivity, low comfort, and mainly without quality of life, which, in many cases, may temporarily leave them unemployed or even condemn them to abandon their career early [ 8, 9].

Among the main causes of the development of WMSD in dentistry are poor posture at work. A study carried out with 1250 dentists from Belgium, Luxembourg, and the Netherlands showed that 64% of the evaluated professionals had disorders in the neck, shoulders, and spine; 42% suffered from headaches; there was a higher occurrence of posture disorders in women; greater occurrence of disorders in dentists over 1.80 m tall; greater occurrence of neck and shoulder disorders among dentists who worked with direct view of the maxilla; and 1/3 of dentists had muscle fatigue. It was also demonstrated that the more difficult the treatment is, the worse the posture, and also that the neck muscles were the ones that most contributed to the occurrence of fatigue and disorders [ 13]. Several studies showed that dentists worked in the same posture for many hours at a time and were very exposed to static body posture. In addition, they use equipment with inadequate lighting and color combinations and are exposed to an irritating sound load, which affects both mental and physical health [ 2, 4, 9, 11, 13].

Jianru et al. found that there was a high prevalence of WMSDs in the neck, trunk, and lumbar region. They also found that professionals who worked in the specialty of periodontics had the biggest complaints in most parts of the body, with the exception of the wrist and knees. The authors concluded that WMSD prevention should be specific to the characteristics of each type of specialty and that risk factor prevention should be introduced as early as possible [ 14].

Currently, there are two theories that guide the adoption of the dentist's working posture in the international scientific literature. The first of them, called classical theory, has been widely used for over half a century, which is defended and predominantly applied in ergonomic training in dentistry courses, both in Brazil and in several other countries around the world [ 5, 15, 16]. This theory proposes a working posture so that the dentist's legs maintain a 90-degree angle in the popliteal region and between the thighs and the abdomen. Furthermore, for the right-handed dentist, this theory proposes that only the dentist's left leg be positioned under the backrest of the patient dental chair and that his right leg remains parallel to the patient dental chair, while the opposite is indicated for the left-handed dentist. Unlike the classical theory, the second theory, more recently proposed by ESDE based on the parameters described in ISO 11226, proposes a seated working posture in which there is a minimum angle of 110 degrees in the popliteal region and between the thighs and abdomen of the dentist. In addition, it also proposes that the dentist's two legs be under the backrest of the patient dental chair, which allows better approximation and freedom of movement for dentists to suit their visual and approach needs in the intra-oral work field. Thus, according to ESDE [ 17], the dentist is allowed to adopt a more dynamic posture, and with greater freedom of approach and movement of the dentist's body around the chair. Consequently, the need for excessive flexion of the upper limbs is reduced, facilitating the adoption of a neutral working posture and with less muscle and skeletal overload. When, for example, the dentist performs dental scaling procedures, it is necessary to visualize the mesial, distal, buccal, and lingual/palatal dental surfaces, which are directed in opposite directions. If there is no freedom of dentist's body movement so that the patient dental surface is positioned in front of the dentist's eyes, the dentist will automatically lean excessively, adopting an awkward posture.

ISO 11.226:2000 Standard, Corr. 1:2006 has been thoroughly evaluated and adapted to the way the dentist works by the European Society of Dental Ergonomics (ESDE). However, after 15 years, no studies were found that showed strong evidence of effectiveness in reducing the prevalence of awkward posture in applying its parameters within the scope of dental practice. Due to the fact that the classical theory has been applied for a long time and the fact that there is no strong scientific evidence, on most dentistry courses, ergonomic training is still based on classical theory, contrary to the requirements and parameters for ergonomic posture proposed by ESDE and ISO 11226. The change in the theoretical foundation in training to adopt a neutral posture at work by dentists is also hampered by the little scientific evidence of the contribution provided by educational interventions on work postures and the prevalence of WMSD.

According to studies by Lindegard et al., Elders et al., Linton and Van Tulder, and Veiersted et al. [ 18, 19, 20, 21], there are inconsistencies, and the scientific evidence of the positive effects of educational interventions on work postures and the prevalence of WMSD is not strong. Studies have shown that there is no evidence that educational interventions in the workplace are effective in reducing complaints and improving performance [ 22, 23]. The great concern about the high prevalence of WMSD and the difficulties related to learning and adopting a healthy work posture led the European Society of Dental Ergonomics-ESDE to publish the document: "Ergonomic requirements for dental equipment. Guidelines and recommendations for the design, construction and selection of dental equipment". These requirements establish the basis for teaching ergonomics at universities, for the design, construction, and selection of dental equipment, and information for dental surgeons to adopt a safe, comfortable, and healthy posture when providing dental care to their patients [ 17, 24].

The close relationship between the disorders that affect dental professionals and their routine activities justifies the relevance of training dentists according to their specialty, to avoid the related symptoms to WMSD and its consequences [ 14]. It is necessary to make dentists aware of preventive measures that can be developed and planned against these disorders, so that they can enjoy a better quality of life [ 1, 2, 3, 10, 14, 15, 18]. Systematic reviews of the literature carried out by Mulimani et al. [ 16] highlight that, in the dental field, there are no studies with strong scientific evidence that ergonomic training is effective for the prevention of work-related musculoskeletal disorders. Similarly, the scientific evidence for the positive effects of ergonomic training on work postures is not strong, and the results of observational studies and rare studies are inconsistent.

Given the above, due to the gap in the area, the aim of this study was to verify the effectiveness of the application of training based on the ergonomic parameters proposed by the European Society of Dental Ergonomics (ESDE) and ISO 11226 in reducing the prevalence of the main awkward postures adopted by female dentists who apply the fundamentals of classical theory during execution of dental scraping on a dental mannequin. Hypotheses of this study are: H0 = Ergonomic training based on ESDE, ISO 11226, and DIN EN 1005-4 parameters which do not interfere with the prevalence of awkward postures; and H1 = Ergonomic training based ESDE, ISO 11226, and DIN EN 1005-4 parameters which reduce the prevalence of awkward postures.

2. Materials and Methods

2.1. Study Type

A randomized clinical trial was undertaken for this study. For the preparation of this document, the Consort Guidelines were followed [ 25]. A fulfilled check-list was provided as a supplementary material (Table S1). This clinical trial has protocol number #11919 in the Brazilian Clinical Trials Registry (REBEC) and can be accessed at: https://ensaiosclinicos.gov.br (accessed on 17 October 2021).

2.2. Ethical Considerations

This study was evaluated and approved by the Ethics Committee in Research with Human Beings of the Bauru School of Dentistry, University of São Paulo, Bauru (São Paulo, Brazil) (CAE: 38821714.4.0000.5417).

2.3. Study Population and Eligibility Criteria

One hundred and eighty (180) female dentists, who were enrolled in training courses at specialization, Master's, or doctoral level, were invited to participate in the study.

Inclusion criteria were having completed a dental course at least 2 years ago, female, and being enrolled in one of the postgraduate courses in the macro region of the city of Bauru, State of São Paulo, Brazil.

Exclusion criteria were: male dentist, neither presenting nor having presented MSD symptoms during the last seven days, not being in the final stages of the gestation period, and that the expected date for completion of the course only occurred after the end of data collection in the final phase (post training).

2.4. Study Sample, Sample Size and random Allocation Procedure

Sixty-eight (68) of the one hundred and eighty (180) invited dentists accepted the invitation to participate in the study (positive response rate of 38%). This study was conducted only with female dentists because they are at increased risk of developing MSD [ 26]. It was considered unfeasible to obtain a sample number of male dentists in the courses that was sufficiently representative for one more variable to be considered in the study. Hence, the research participants were all female dentists, with completion of the dental course of at least 2 years. The minimum age of participants was 24 years and the maximum were 45 years, with a mean of 27.48 years (SD 4.62 years). All of them were graduates in dentistry and were enrolled in one of the specialization courses, i.e., Masters or doctorates at the Faculty of Dentistry of Bauru (FOB/USP), or in Dental Education Institutes, Training Centres, and Class Associations in the region of Bauru, São Paulo, Brazil.

The random allocation of participants to each group was performed by two researchers (ESO and AVSSC) in an attempt to ensure that the researcher responsible for assessing outcomes and data analysing was blinded. Random allocation procedure was performed by using the Excel software of the Office Package version 2019. First, a code was assigned to each participant, numbering from 1 to 68. Then, in an Excel spreadsheet, a column labelled as "ID_Part" was created, and then a number sequence was created in the lines of that same column between 1 and 68. Then, another column labelled as "Group" was created, and, by applying the function "=RANDBETWEEN(0;1)", the codes 0 or 1 were assigned to each line. Participants who received code zero were allocated to the control group and those who received code 1 were allocated to the intervention group. Finally, a descending classification was made based on the column group, where it was found that 29 participants were assigned to the intervention group. Therefore, the code of the first participant was manually changed from code 0 to code 1, so that 30 participants were assigned to the intervention group and 38 to the control group, resulting in allocation ratio of 0.8.

The quantitative dependent variable was obtained by the total sum of awkward postures; thus, data analysis was performed using generalized linear models, applying the generalized linear models method, the generalized estimated equation, with Poisson distribution and with log link function. Thus, 20 participants per group were determined as the minimum sample size [ 27]. Considering the possibility of losses due to participant abandonment during the research period, 30 participants were decidedly allocated to the intervention group and 38 to the control group.

Figure 1 presents flow chart of participants enrolled in the study and the logistics regarding the two groups, as follows:

CG (control)-composed of 38 professionals who received training only at the end of the study.

IG (intervention)-initially composed of 30 professionals, 8 of whom declined to participate in the research for various reasons, and 22 professionals remained so. These were given the theoretical and practical ergonomic training proposed by ESDE ( Supplementary Material). This training was based on the principles described in the document "Ergonomic requirements for dental equipment. Guidelines and recommendations for designing, producing and choosing dental equipment" [ 17]. This document was based on the Norms ISO 6385: 2004 (E), DIN EN 1005-4, and ISO 11226: 2000-Cor.1: 2006 (E), and their applicability to the dental practice [ 28, 29, 30].

2.5. Phase 1 (Baseline)

This phase was carried out from March to September 2016.

No ergonomic guidelines were given regarding the professional's posture or how to correctly position of the work field in this phase.

A phantom head (Pronewodonto ®-BOB model) was adapted to be properly attached to the patient's dental chair ( Figure 2A) to allow the necessary adjustment of height and head movements in three directions, as proposed by ESDE [ 17].

The participants were instructed and monitored regarding to the limits of motion of the phantom head ( Figure 2B). Participants in both groups were asked to perform dental scaling procedures on six dental surfaces: buccal surfaces of teeth 16, 11, 26, and 31, and lingual surfaces of teeth 36 and 46 ( Figure 2C). To facilitate the control and identification of the proper use of each dental curette to each tooth surface, the tooth surfaces were previously covered with red nail enamel for anterior teeth and a blue one for posterior teeth. Dental curettes were also identified with the same colors according to the indications for use on each surface to be cleaned ( Figure 2 D).

All observations were performed by using 5 video cameras ( Figure 3A), fixed 1 m away from the research participant, with the exception of Camera 5, which was moved by the researcher at a certain variable distance. Table 1 shows parameters analyzes according cameras. Camera 1 (right side view- Figure 3C): arching of the trunk or convex lumbar lordosis (parameter 4), the frontal inclination of the trunk (parameter 5), arm flexion (requirement 9), flexion of the forearms (parameter 11), and the angulation of the popliteal region (parameter 12). For Camera 2 (Back view- Figure 3D), the following were evaluated: lateral trunk flexion (parameter 6), shoulders raised (parameter 8), and abduction of the arms (parameter 10). For Camera 3 (left side view- Figure 3E), the following were evaluated: the frontal inclination of the head (parameter 2) and neck flexion (parameter 3). For Camera 4 (upper view- Figure 3F), the following were evaluated: lateral flexion and rotation of the head (parameter 1), and trunk rotation (parameter 7). The leveling of the cameras was carried out and monitored constantly with bubble level devices, attached to the base support of the cameras ( Figure 3B). In addition, in order to facilitate data recording and analysis, a transparent acrylic support was built on which the parameters and limits of angular inclinations of the body segments were printed ( Figure 3 B). The support that was fixed frontally to all cameras, with the exception of Camera 5 (overview), which was used only to support the researcher to reduce possible uncertainties during data collection.

A dental surface scaling time of 20 s was established for each dental surface, monitored by the researcher, and so each participant performed the dental scaling for a total time of 120 s. The outcome variable was defined as the sum of all "Awkward Postures" (yes/no) attributed to each of the 12 requirements assessed.

Table 1 presents the angular parameters applied to classify the postures of the head, neck, and trunk into three types according to international standards, as follows [ 26, 29, 30]:

Neutral posture (acceptable)-when the inclinations were within the minimum limit;

Moderate static posture (unacceptable)-when the maximum holding time (MHT) lasts for four or more seconds), and;

Awkward static posture (unacceptable)-when the slopes are greater than the extreme limit.

MHT is a measurement related to static muscle work and represents the maximum time during which a static muscle load can be maintained while adopting moderate posture. ISO 11226 includes a relationship between inclination and maximum acceptable holding time, which was defined as 20% of maximum holding time-MHT [ 29, 31, 32]. Ohlendorf et al. considered that the static body posture is defined as a posture that is being held for more than four seconds [ 33].

Other studies considered the specificities and physiological requirements for the proper performance of tasks in dental practice, thus corroborating the application of these angular parameters and their relationships with the MHT and classification of the types of static postures [ 4, 17, 32, 33, 34, 35].

Thus, in this study, to analyze head, neck, and trunk inclinations, the value of 20% of MHT was applied when the angular limits of neutral posture were exceeded, without, however, reaching the extreme angular limits of awkward postures.

Hence, in this study, four seconds was determined as MHT for moderate postures, a value that corresponds to 20% of the total dental scaling time for each dental surface.

To analyze the flexion and abduction of the upper arms, the relationship between inclination and maximum acceptable holding time specified by ISO 11226 was applied [ 29].

The parameters of back rounded backwards (C-shaped back), raised shoulders, flexion, and knee angle forearms and trunk-to-thigh angle were based on ESDE [ 17].

As can be seen in Figure 3 G, dentists in both groups were provided with a dental stool (Manufacturer Dabi Atlante, standard model, with sloping seat front edge) that allows them to work with seat inclination between 90 degrees to 110 degrees in the popliteal region and between the thighs and abdomen. However, the training given to the intervention group emphasized the benefits of working with an angle of at least 110 degrees.

The analysis of the videos was performed by two researchers (ESO and AVSSC). To improve the reliability of the results, training and analysis calibration of ten (10) videos of simulated periodontal procedures were performed. The videos were recorded during data collection in phase 1. First, each of the 12 parameters were reviewed, discussed, and doubts about the classification criteria, such as neutral, moderate, and awkward posture were clarified, based on the parameters proposed by ESDE, ISO 11226, and DIN EN 1005-4. Next, by using a check-list of the 12 ergonomic parameters the 10 videos were evaluated separately by each of the researchers. In order to facilitate counting the maximum holding time (MHT) on each of the tooth surfaces, the video editing software AVS Video Editor V. 7.2.1 was used. Then, a meeting was held to present and discuss each classification attributed by the researchers to each of the 12 parameters evaluated in the 10 videos evaluated. The results presented by each researcher were compared and the differences were discussed until reaching a consensus, which was considered the "gold standard". Cohen's unweighted Kappa test was applied, obtaining values of 0.92 and 0.89 for the ESO and AVSSC researchers, respectively. These Kappa values revealed that the level of agreement reached was excellent and certified that the analysis criteria were properly applied in accordance with the criteria and parameters recommended by ESDE, ISO 11226, and DIN EN 1005-4. It should be clarified that one of the video evaluators (ESO) actively participated in the discussions and analyzes on the applicability of ISO 11226 to the conditions, specificities, and ways of working with dentists. This participation took place at the ESDE annual meetings held in 2002, 2003, 2005, and 2006 and provided in-depth knowledge about the adoption of a correct working posture, in accordance with ISO 11226 and DIN EN 1005-4. This allows us to infer that a larger number of evaluators would have a limited contribution to increase the reliability of the results.

2.6. Phase 2

This phase was carried out from September 2016 to February 2017.

IG ergonomic training (intervention) was carried out through theoretical activities, consisting of a presentation of the requirements for adopting a healthy work posture and presentation and provision of demonstrative video. The training activities were carried out in postgraduate clinics, in accordance with the European Society of Dental Ergonomics protocol [ 17].

Recording videos of the procedures performed by IG participants. Recording videos of the procedures were performed by the CG. To benefit all research participants, the CG (control) also received ergonomic training after the study was completed.

2.7. Data Analysis

IBM SPSS Statistics 27 was used for the exploratory and descriptive statistical analysis of the awkward posture total score and of the 12 requirements separately. The level of significance was set at α = 0.05 for all statistical tests performed. Since the awkward posture total score data were not normally distributed, the generalized linear models, by applying generalized estimated equation (GEE) with Poisson distribution and log link function, were used. The comparison graphs of the 12 requirements between groups, before and after training, were performed using mixed generalized linear models and settings between subjects were used as a random effect. The network analyses were conducted with RStudio (R Core Team, 2019), using R packages qgraph, huge, bootnet, and EGAnet. Estimating Ising models required supported methods to maximize pseudo-likelihood. Estimate type of network is Ising Networks.

3. Results

In the initial time, 720 observations were performed in the 2 groups, 525 (73%) out of presented awkward postures. In the final phase, 720 observations were also made, 403 (56%) out of showing awkward postures, of which 328 (72%) were of the control group and 75 (28%) of the intervention group. In total, comprising the two phases, 1440 observations were performed, with 528 (37%) from the intervention group and 912 (63%) from the control group.

Table 2 shows the statistical analysis of the effectiveness of the ergonomic training on the intervention group compared to that of the control group. The training was effective, showing a statistically significant difference (p < 0.001) when compared to the control group and intervention group before training.

The distribution of the prevalence of awkward postures according to the groups and also according to the initial and final phases is shown in Figure 4. Although there is a slightly larger amount in the initial intervention group, there were no significant differences among the groups initial control, initial intervention, and final control. On the other hand, there was a statistically significant difference after training of the intervention group, which resulted in a significant decrease in the adoption of awkward postures ( Table 2 and Figure 4).

Figure 5 shows the distribution of the differences between the final minus initial score of the awkward postures according to the groups. The effectiveness of the training can be noticed since, in the intervention group, the differences were negatives (less than zero), and only one subject presented no improvement (difference equal to zero). On the other hand, in the control group, verified a substantial number of subjects with an equal or higher scores in the final phase was verified, resulting in a no or greater than zero difference.

Images 1 to 12 of Figure 6 reveal that, in only three of the twelve posture requirements which evaluated the ergonomics training, there were no statistically significant differences between the control and intervention groups. Regarding inadequate neck flexion postures greater than 25 degrees (requirement 3), we found that there was a marked decrease in both the intervention and control groups, with no statistically significant difference (p = 0.330) after ergonomic training in the intervention group. A similar situation occurred with inadequate postures of upper arm flexion greater than 25 degrees (requirement 9) and upper arm abduction greater than 20 degrees (requirement 10), in which statistical significances were p = 0.565 and p = 0.699, respectively.

Figure 7 and Figure 8 shows results from the analysis of networks, which were randomly distributed in the control and intervention groups at phase 1. Networks comprise graphical representations of the relationships (edges) between variables (nodes). Network analysis provides the capacity to estimate complex patterns of relationships and the network structure can be analysed to reveal core features of the network.

Neutral working posture is achieved through the balance of muscle forces that act in a kinematic chain. Hence, network analysis was applied to detect relationships between requirements, i.e., between types of awkward postures, according to phases and groups. Nodes represent variables (requirements) and undirected weighted blue edges show positive relationships (e.g., positive correlation/covariance between variables) while red ones show negative relationships. The strength of relationships is demonstrated by the thickness and colour density of the edge connecting the nodes; thicker denser coloured lines indicate stronger relationships.

Variable 8 (raised shoulders) had great importance in both groups, as seen in Figure 7. In relation to phase 1 and 2, in both groups, the relationships between the variables were maintained, only with a modicum of correlation forces, especially in the intervention group where the relationships were weaker.

4. Discussion

In the present study, the effectiveness of ergonomic training based on the parameters and requirements proposed by ESDE [ 17], ISO 11226 [ 29], and DIN EN 1005-4 [ 30] to decrease the prevalence of inadequate postures adopted by female dentists was verified, compared to those that apply the fundamentals of classical theory during the execution of scaling procedures periodontal. Findings of this study reveal that ergonomic training based on ESDE, ISO 11226, and DIN EN 1005-4 parameters and requirements resulted in a statistically significant overall decrease of 63 percent in the prevalence of awkward postures in relation to most requirements analysed.

The same did not happen with the control group, which, although it showed a small improvement in some requirements, was not statistically significant. This fact is important because, in the interval between the initial and final time, participants from both groups could have integrated new knowledge of ergonomics, which would be an external factor to the research. Thus, we can affirm that the difference found in the intervention group was not due to interference outside the study; otherwise, it would also have occurred in the control group.

In the initial phase, considering the two groups, there was a high frequency of non-recommended postures, corroborating the results found by several authors [ 13, 18] who also found high percentages of non-recommended working postures practiced by professionals which are mainly responsible for high levels of WMSD prevalence [ 26]. Ergonomic training resulted in a decrease in the amount of non-recommended postures by 63% overall. There was a 100% reduction in the requirements for the frontal trunk flexion and angle in the popliteal region of less than 110 degrees and, therefore, a complete improvement due to the application of training.

According to Bridger et al. [ 37], this allows a neutral posture and concavity in the lower back of the spine to be maintained because it prevents the pelvis from tilting back more than 6.3 degrees. This result corroborates the results achieved by De Bruyne et al. [ 31, 38], in which the influence of different types of owls on muscle activity and on lumbar posture was investigated. Twenty-five participants completed a sham dental procedure in a standard stool (90-degree popliteal region), a saddle-type stool, and the Ghopec stool (both allow more than 110 degrees in the popliteal region). The Ghopec stool, which meets the requirements proposed by ESDE, has a seat consisting of a horizontal rear part to support the pelvis and a downwardly sloping front part to support the upper legs, and a backrest for the legs. Vertically and horizontally adjustable back. The results of this study revealed that the lumbar posture was closer to neutral in the Ghopec stool, while sitting in a standard and in the saddle stools resulted in more flexed and extended lumbar postures, respectively.

Sitting at a 90-degree angle in the popliteal region (standard stool) resulted in greater activation of the back muscles while sitting at a 125-degree angle (saddle and Ghopec stool) activated the abdominal muscles more, although less in the presence of a backrest (Ghopec). According to de Bruyne et al., in order to maintain a neutral posture while performing dental procedures, the Ghopec owl is considered the most suitable design for the tasks performed [ 38]. The results of this study corroborate the findings of De Bruyne et al., (2016) and ESDE recommendations (2007) because they showed that trained dentists presented a significant decrease in the prevalence of awkward postures. This was mainly due to the change promoted by increasing the angle from 90 degrees to 110 degrees in the popliteal region and between the thighs and abdomen, with the dentist sitting on a dental stool provided with an inclination of the front of the seat by about 20 degrees and with an adequate backrest for the back.

The results found in relation to the requirements of flexion of the head and flexion of the neck showed an improvement of 56% and 68%, respectively. Lindegard et al. [ 18] concluded that the reduction in head and neck flexion can be achieved with the use of prismatic glasses, with the advantage that these devices do not have limitations related to focal length, as occurs with the use of magnifying glasses. Additionally, in the study by Hayes et al. [ 39], the researchers concluded that the use of magnifying glasses did not reach conclusive results about the benefits of using these devices in relation to improving head and neck posture.

The non-recommended positions of the head, trunk, shoulders, arms, and forearms could have achieved better results if the participants had correctly positioned the field of work. In this study, a mannequin was used, eliminating the professionals' concern with the patient's discomfort and, additionally, reducing interference regarding the possibilities of correct positioning of the work field, due to the inexistence of possible limitations inherent to the difficulties in moving the head of real patients. Despite this, similarly to what happens with a real patient, the research participants did not perform the proper movement of the mannequin's head, which resulted in the incorrect positioning of the work field and the resulting adoption of an inadequate posture by the professional. In a study carried out with workers in a steel processing plant, Delleman [ 40] analysed the ideal mechanisms for adopting postures in relation to the work field. Guidelines on working height were formulated in order to minimize the load on the musculoskeletal system and it was found that the ideal distance from the working field to the visual field must be 35 cm. At this distance it is not necessary to flex the head and neck inappropriately to gain a view of the working field.

Botta et al. [ 41] conducted a cross-sectional study with dental students and found that they had a limited perception of risk factors. The lower the academic level of students, the greater their perception of risk factors that can contribute to musculoskeletal disorders. According to the authors, first-year students pay more attention to the risk factors they are exposed to when compared to senior students due to lack of clinical experience and concluded that more studies are needed to identify the most appropriate ergonomic program. In our study, we observed that dental surgeons, when receiving ergonomic training, obtain an improvement in relation to correct positioning, so training for the adoption of an ergonomic posture is an intervention strategy that needs to be carried out in order to reduce the prevalence of inappropriate postures.

This study was carried out with mostly female young professionals, who were students in specialization, Master's, and doctoral courses in several areas. According to the Federal Council of Dentistry of Brazil (CFO), approximately 217,000 (60%) of the 361,981 registered dentists are women and the proportion of women has been increasing steadily in recent decades [ 42]. These data corroborate those reported by Ohlendorf et al. [ 26] which reveal the growing proportion of female dentists in several countries, and also demonstrate that women are more susceptible to developing MSD. Hence, in this study, the impact of training based on ISO 11226 and DIN EN 1005-4 parameters only on female dentists was chosen for study, aiming to reduce the confounding effect of a reduced number of male dentists registered in dental courses where the training was carried out. For this reason, the results found in this study are limited to female dentists, and a recommendation is to develop additional studies that also cover male dentists.

A high prevalence rate of awkward posture was found in both control and intervention groups, in the initial time, before training. This demonstrates that the knowledge of dental ergonomics based on the classical theory of the dentist's sitting working posture acquired and retained in graduation was not sufficient for female dentists to adopt a neutral sitting working posture. It was also found that the performance of ergonomic training with emphasis on current knowledge can contribute to a decrease in the adoption of awkward postures. Most likely, Master's and doctoral students will also be future professors and researchers; this fact reveals that, in order to change the current epidemiological profile of MSD in dental practitioners, the appropriate teaching of dental ergonomics needs to be stimulated and promoted in undergraduate, specialized, Master's, and doctoral courses, thus corroborating the findings of Jianru et al. [ 14]. Additionally, the dental scaling procedures performed in this study are performed with high frequency in the practice of general dentistry and in the specialty of periodontics, which makes these findings of special importance for dental professionals in these specialties.

The analysis of the network offers the opportunity to advance in elucidating the dynamics of the muscular kinematic chain responsible for the posture adopted during the performance of dental treatments. Network analysis is a promising field of research should be applied in network analysis to longitudinal data [ 43, 44]. Through this type of analysis, we seek to better understanding of the changes in the associations between the 12 posture requirements over time, that is, before and after training. In the present study, we observed the relationships between variables that had a slightly different initial distribution in the control and intervention group, but with strength in the variable and the correlation decreased from time 1 to 2 in the intervention group.

The results found through the network analysis revealed the existence of a significant relationship between the body segments evaluated and that the ergonomic training produced positive changes in this relationship. These findings corroborate Hokwerda et al. [ 21] who stated that, to perform dental procedures, it is necessary for the dentist to have adequate hand-eye coordination, achieved through a kinematic chain composed of several body segments that must move in an ideal coherence in the space before the upper body of the dentist. This kinematic chain consists of the fingers, hands, forearm and arm, upper body, shoulders, neck, and head, which incorporates the viewing direction of the eyes. In order to carry out the different tasks, visual, tactile, and proprioceptive perception is necessary. Furthermore, according to Hokwerda et al. [ 17], the information collected is processed and the output generated, directed towards the movement of the kinematic chain, with the hand and fingers at the end of the chain to carry out the tasks.

The network analysis in the IG revealed that working with raised shoulders (requirement 8) and neck flexion greater than 10 degrees (requirement 3) presented greater centrality, thus demonstrating a stronger level of relationship with the others posture requirements. After training, there was a significant inactivation of the negative relationship between requirements 8 and 12, revealing that the adoption of a posture with knee angle and trunk-to-thigh angle between 110° to 135° significantly contributed to reduce shoulder raising ( Figure 6(12) and Figure 7). However, training did not significantly contribute to improvement in relation to neck flexion (requirement 3), which can be explained by its weak or non-existent relationship with requirement 12. This corroborates the recent findings of the study conducted by De Bruyne et al. [ 45] who demonstrated that just working seated higher is not enough to improve neck posture. In this study, dentists were not given the option to wear prismatic glasses or magnifying glasses. Hence, it was not possible to assess the corroboration with the findings of the study of the Lindegard et al. [ 18, 46] which demonstrated that using glasses with a prism segment so that there is a reduction in the angle of the operator's neck during the execution of dental treatment and also to reduce neck pain significantly more at follow up compared with the reference group.

This study highlighted the importance of using the network analysis method for a better understanding of the relationships of the body segments promoted by the kinematic muscle chain and its balance for the adoption of a neutral working posture. Additional studies using this method can contribute to deepen in the knowledge on the dynamics of the kinematic muscle chain when performing dental treatment.

Gathering and analysing data by using a control group in the initial and final phases allowed to minimize some limitations of possible external interference. It was not possible to perform blinding because our intervention required training for only one of the groups. The behaviour of the participants may have changed favourably, due to the awareness of participating in the research, as the participants were being observed and filmed, leading them to adopt a different posture from the usual one. This phenomenon is known as the Hawthorne effect, which may have produced a synergism effect, enhancing the decrease in the prevalence of non-recommended postures and, therefore, the results achieved may be overestimated [ 47]. However, some factors suggest that the chances that the results were influenced by factors outside the study are small. The fact that data collection and analysis was performed in both control and intervention groups, in the initial and final time, was a way to detect the impact of possible external interferences to the study, such as the access of research participants to classes, videos, and content about dental ergonomics. Additionally, it is also positive that the groups were quite homogeneous in relation to several factors such as gender (all participants were female), also due to similarity in terms of age, current context of life, daily routine divided between postgraduate studies, and providing care to their patients in the dental office.

Furthermore, the similar results obtained in the two groups in the initial time and also the similarity of the results in the control group in the initial and final times allow us to infer that it is unlikely that there was any kind of interference external to the research that interfered in only one of the groups. This was also due to the fact that both groups received guidance on the research objectives and on the conditions for developing the observations, and finally the fact that the participants of both groups were influenced by being aware of being filmed while performing dental scaling. Otherwise, there would have been a low prevalence of awkward postures also in the initial time.

This study was based on the assumption that the participants at the beginning of this study, both in the control group and in the intervention group, had not updated knowledge on the subject. Based on the so-called classical theory of sitting posture in dental work, research and teaching of dental ergonomics in dentistry courses in Brazil were very successful between the 70s and 90s. Research on dental ergonomics was accentuated. As a result, in most courses, the content taught today is practically the same as it was about 40 to 50 years ago, without therefore following the evolution of knowledge that took place in the last two decades, which was not effectively transferred to teaching practice by the great most teachers in the area in Brazil. The results achieved confirmed the premise that it is necessary to strengthen research and teaching of dental ergonomics for the dissemination of new knowledge in teaching practice and in the daily lives of future dentistry professionals. Therefore, in the current context of teaching dental ergonomics both in Brazil and internationally, applied training actually represents a paradigm shift between two opposing foundation theories, namely the classical theory and the one based on the new parameters based on ESDE, ISO 11226, and DIN EN 1005-4.

This study was conducted using a personalized methodology developed by its researchers due to the impossibility of accessing high technology, such as the use of accelerometers and advanced information technology systems. However, despite the simplicity of the method employed, all precautionary measures were taken to ensure the reliability of the angular and time measurements, which were confirmed by the excellent results achieved in the training and calibration process of the examiners. Thus, the use and presentation of a methodology with characteristics of simplicity, low cost, and the feasibility of obtaining high reliability results is a great contribution brought by this study. Such characteristics increase the possibilities that other researchers with similar conditions have the possibility of developing studies in the field of dental ergonomics, even if they have little or no access to resources and methods with high added technology and at high cost.

Another important contribution of this study, from the perspective of the researchers of this study, is the fact that its results reveal that practically all of the dentists are at high risk of developing MSD because they have neither access nor to current advances in ergonomic knowledge, nor to ergonomically improved equipment to minimize such risks. This study corroborates with studies published in the scope of ESDE and makes a significant contribution to the development of knowledge about dental ergonomics, considering the importance of knowing the real limitations in coping with and reducing the burden and suffering of dentists resulting from MSD.

Although the Nordic Musculoskeletal Symptoms Questionnaire was not applied, when questioned, all study participants declared that they had not had symptoms of WMSD, pain, or discomfort in the last twelve months. It is recommended that similar studies should be carried out using digital accelerometers, which allow for greater ease and increase objectivity regarding the measurement of inclinations in the various body segments. Thus, obtaining numerical variables in an automated way will allow the use of statistical techniques that have even detail and specificity regarding the benefits due to the training of dentistry professionals.

5. Conclusions

It was concluded that the ergonomic training based on the parameters of ISO 11226 and DIN EN 1005-4, as well as its adaptations to the dental practice provided by the European Society of Dental Ergonomics and other recent studies, contributed significantly to reducing the prevalence of awkward postures adopted by female dentists during the simulation of the basic periodontal procedures. However, it was not effective enough to improve the posture of the head and neck.

Supplementary Materials

Author Contributions

Conceptualization, A.V.d.S.S.C. and E.S.O.; methodology, A.V.d.S.S.C., D.M.B.N. and E.S.O.; formal analysis, A.V.d.S.S.C., E.S.O. and E.M.C.; data curation, A.V.d.S.S.C., S.H.d.C.S.-P., A.R.d.F.A. and G.A.F.J.; writing-original draft preparation, A.V.d.S.S.C., R.L.B., D.V.B. and E.S.O.; writing-review and editing, E.d.S.B.M.P. and R.L.B.; visualization, L.C.P.; supervision, E.S.O. All authors have read and agreed to the published version of the manuscript.

Funding

The present study was financed in part by the Coordination for the Improvement of Higher Level Personnel (CAPES)-Finance Code 001, and National Council for Scientific and Technological Development (CNPq)-Process 304619/2018-3.

Institutional Review Board Statement

The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board (or Ethics Committee) of Bauru School of Dentistry (protocol code CAAE 38821714.4.0000.5417, opinion number 970.770 and date of approval 3 March 2015).

Informed Consent Statement

Informed consent was obtained from all subjects involved in the study.

Data Availability Statement

The data presented in the present study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

References

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Figure 2. Attachment of the phantom head to the patient's dental chair and organization of the dental procedure. ( A) Phantom head attachment to the patient's dental chair; ( B) Control of the phantom head motion by means of boundary lines; ( C) Dental surfaces to be cleaned; ( D) Identification of anterior and posterior curettes by means of colors.

Figure 3. Device built to support cameras 1 to 4, camera 5 positioning and views obtained by each of the cameras. ( A) Positioning of the 5 cameras; ( B) Transparent acrylic support with the parameters and limits of angular inclinations and bubble levels to keep cameras straight; ( C) Right view; ( D) Back view; ( E) Left view; ( F) Upper view; ( G) Overview camera.

Figure 6. ( 1- 12) Comparison of the awkward posture prevalence between groups and phases, according to 12 accessed parameters.

Table 1. Parameters used as limits of inclination, according to the body segment and positioning of cameras used for evaluation [ 4, 17, 29, 30, 32, 33, 36].

Parameters According to Body Segment

Angle Range Values According to Ergonomic Standards

Camera Position

Neutral

Moderate *

Awkward

4-Back rounded backwards (C-shaped back)

visual check of the back shape

Right

6-Trunk lateral inclination

−10 to 10°

−10 to −20°
&
10 to 20°

<−20° or >20°

Backward

8-Raised shoulders

visual check of the shoulders shape

Backward

Group

Time

Estimated Marginal Mean of Non-Compliance Score

p-Value *

Wald 95% CI for the Mean

Lower

Upper

Control

Initial

8.632

0.598

7.937

9.386

Final

8.211

7.385

9.128

Intervention

Initial

8.955

<0.001

8.036

9.978

Final

3.409

2.747

4.231

# data[].attributes.attachment_link.title
Effectiveness of Ergonomic Training to Decrease Awkward Postures during Dental Scaling Procedures: A Randomized Clinical Trial

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Studies demonstrate that there is a lack of effective ergonomic principles for adopting a neutral posture during the execution of dental procedures. ISO 11.226:2000 Standard, Corr. 1:2006 has been thoroughly evaluated and adapted to the way that dentists work by the European Society of Dental Ergonomics (ESDE).

# data[].attributes.attachment_link.title
Decoding the ergonomics in the new normal for dentistry: A narrative review | Munjal | Journal of Education Technology in Health Sciences

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Decoding the ergonomics in the new normal for dentistry: A narrative review

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Academic Editors: Ignacio Pavón García, Juan Manuel López and Nélson Costa

Received: 16 December 2021 / Revised: 11 January 2022 / Accepted: 14 January 2022 / Published: 21 January 2022

Background: In general, the prevalence of work-related musculoskeletal disorders (WMSD) in dentistry is high, and dental assistants (DA) are even more affected than dentists (D). Furthermore, differentiations between the fields of dental specialization (e.g., general dentistry, endodontology, oral and maxillofacial surgery, or orthodontics) are rare. Therefore, this study aims to investigate the ergonomic risk of the aforementioned four fields of dental specialization for D and DA on the one hand, and to compare the ergonomic risk of D and DA within each individual field of dental specialization. Methods: In total, 60 dentists (33 male/27 female) and 60 dental assistants (11 male/49 female) volunteered in this study. The sample was composed of 15 dentists and 15 dental assistants from each of the dental field, in order to represent the fields of dental specialization. In a laboratory setting, all tasks were recorded using an inertial motion capture system. The kinematic data were applied to an automated version of the Rapid Upper Limb Assessment (RULA). Results: The results revealed significantly reduced ergonomic risks in endodontology and orthodontics compared to oral and maxillofacial surgery and general dentistry in DAs, while orthodontics showed a significantly reduced ergonomic risk compared to general dentistry in Ds. Further differences between the fields of dental specialization were found in the right wrist, right lower arm, and left lower arm in DAs and in the neck, right wrist, right lower arm, and left wrist in Ds. The differences between Ds and DAs within a specialist discipline were rather small. Discussion: Independent of whether one works as a D or DA, the percentage of time spent working in higher risk scores is reduced in endodontologists, and especially in orthodontics, compared to general dentists or oral and maxillofacial surgeons. In order to counteract the development of WMSD, early intervention should be made. Consequently, ergonomic training or strength training is recommended.

1. Background

Dental professionals frequently suffer from work-related musculoskeletal disorders (WMSD). Both dentists and dental assistants have a high prevalence of WMSD, especially in the neck and the trunk as well as in the upper limbs [ 1, 2, 3, 4, 5]. It has been suggested that forced postures that are statically maintained during the dental work are a major hazard for WMSD in dental professionals [ 1, 2, 4, 6]. While the patient is lying supine on the treatment chair, the dentist (D) and dental assistant (DA) sit adjacent to the patient, and are required to gain a sufficient line of sight into the narrow mouth. A static neck and trunk flexion of more than 30° [ 7, 8, 9, 10], a simultaneous lateral flexion and/or rotation to the right in the trunk [ 9, 10, 11], and shoulder abduction [ 7] have been described as typical working postures in dental professionals.

However, in the available kinematic investigations, scarcely any differentiation between the specialized treatment procedures has been explored [ 12]. As the dental treatment profile is vast, specializations are common; for example, generalists, orthodontists, oral surgeons, and endodontologists apply different techniques, and their typical working days are scarcely comparable. It can be expected that the dental task (e.g., extraction of a tooth or the preparation of a tooth) determines the posture, and the duration that the posture is maintained, within that task. However, it can be shown that the performance of the same activities within four different dental work concepts does not cause any noteworthy posture-relevant differences [ 13].

Although there are numerous studies on the prevalence of WMSD and ergonomic interventions [ 1, 2, 3, 5, 9, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27], differentiations between the fields of specialization (e.g., general dentistry, endodontology, oral and maxillofacial surgery, or orthodontics) in these studies are rare [ 28, 29]. Uppada et al. [ 29], for example, found that oral surgeons show a higher prevalence of WMSD than generalists, while Newell and Kumar [ 28] argued for a different ergonomic load in orthodontists compared to generalists. According to both research, generalists work on posterior molars and, therefore, have to spend more time in a bent-over position while orthodontists work rather superficially and can maintain a more upright posture [ 28, 30]. Meanwhile, it remains unclear whether orthodontists suffer less from WMSD than generalists [ 30], or if the extent is similar [ 20].

For all fields of specialization, one may speculate that the patient's head is arranged in such a way that the dentist has the best possible sight into the mouth. In four-handed dentistry, however, the DA for the majority of their time sits opposite the D and, potentially, has to sacrifice posture to a greater extent than the D in order to see into the mouth. Although, to our knowledge, this has not been compared before, survey data show that DAs have a higher prevalence of WMSD than Ds [ 24, 31], and that different body regions are affected [ 9].

In general, the prevalence of WMSD in dentistry is high [ 1, 3, 4, 32, 33] and WMSD are a major cause for ill-health retirement [ 16, 34]. The characteristics of dental work are known to be responsible for an increased prevalence of WMSD in dentistry, such as the profession of dentistry per se, missing breaks, the work schedule, the number of patients treated and certain activities, such as teeth polishing [ 1]. Thus, it is crucial to gain more insight as to whether there are differences in the ergonomic risks of the different fields of specialization.

The Rapid Upper Limb Assessment (RULA) [ 35] is a well-known method for the evaluation of the ergonomic risk as, in addition to assessing the neck, trunk, and upper limb postures, it also considers whether a working process has static or dynamic movement sequences. Lately, an application of the original paper-pen method for an automated use of kinematic data has been published by Vignais et al. [ 36, 37]. This offers an objective and precise approach for the evaluation of the ergonomic risk in real-world conditions with inertial motion capture (IMC) [ 38]. The rapid development of IMC systems has rendered the captured data sufficiently reliable and precise for scientific application [ 39, 40].

This study is part of the SOPEZ project: "Study for the optimization of ergonomics in dental practice" [ 6], having the current aim to compare the ergonomic risk of Ds and DAs in the practices of oral surgeons, endodontologists, general dentists, and orthodontists when performing typical dental procedures. Parts of this project with dental students [ 41] have already been published.

The character of the current investigation is clearly explorative, nevertheless, two main research questions were to be answered: (a) Is there a difference in the ergonomic risk between the four dental fields of specialization for Ds and DAs, respectively? and (b) Is there a difference regarding the individual field of specialization in the ergonomic risk between the Ds and DAs?

2. Materials and Methods

2.1. Subjects

2.2. Dental Tasks

2.3. Measurement System

2.4. Rapid Upper Limb Assessment (RULA)

2.5. Measurement Protocol

2.6. Data Analysis

3. Statistical Analysis

Socio-demographic data were calculated for each field of specialization, respectively. For this purpose, data were tested for normal distribution using the Kolmogorov-Smirnov-Lilliefors test. Since the subject's data were normally distributed, the mean and standard deviation were calculated. The kinematic data were not normally distributed. Therefore, non-parametric tests were applied. For calculating the differences between the fields of dental specialization, the Kruskal-Wallis Test with multiple comparisons was employed.

Due to the exploratory approach in evaluating the kinematic data, a Bonferroni correction was not applied.

The significance level was set at α = 5%.

4. Results

4.1. Differences between the Fields of Dental Specialization

4.2. Dental Assistants

4.3. Dentists

4.4. Differences in the Ergonomic Risk between Dentists and Dental Assistants According to Their Field of Dental Specialization

4.5. Oral and Maxillofacial Surgery

4.6. Endodontology

4.7. General Dentistry

4.8. Orthodontics

5. Discussion

The objectives of the present analysis were to examine the differences in ergonomic risk in four dental specializations for Ds and DAs, and to determine whether there is a difference in the ergonomic risk between Ds and DAs in each specialization.

Regarding the final score of both the right and the left body side, the DAs especially showed higher differences within the fields of specialization. The results revealed significantly reduced ergonomic risks in endodontology and orthodontics compared to oral and maxillofacial surgeons and general dentistry ( Figure 3). Dentists showed comparable results regarding the final score with a reduced magnitude of difference, revealing significant differences only between orthodontics and general dentistry ( Figure 3). Nevertheless, also for dentists, the values of the ERP indicate a clear trend that the ergonomic risk in endodontology and orthodontics is substantially lower than in oral and maxillofacial surgeons and general dentistry ( Table 3).

With regard to orthodontists, it must be taken into account that the results can diverge in cases involving the insertion of lingual or palatally inserted appliances or, for example, TPA, Quadhelix, or GNE; nevertheless, this comparison does not form part of the present study.

However, these results were not observed in the individual body segments. Concerning the dentists, specialization differences are present in the neck, right wrist, upper right arm, and left wrist, with orthodontists having the lowest scores ( Figure 3). However, for the dental assistants, differences in the right wrist and right and left forearm tended to be reversed; almost universally, the score here was worse for orthodontic assistants than for other specialties (except of the right wrist). For the trunk and the right and left forearm, there are no differences between the four specializations in either profession. In this context, it must be taken into account that right-handed persons were analyzed and, thus, the right hand is also the leading working hand.

If all significant differences between the specializations of the Ds and DAs are considered together, the relative average risk score over the time for the final score right and left and the individual segments in the field of endodontics and orthodontics is almost always lower than in the other specializations. In oral and maxillofacial surgery, on the other hand, the relative average risk score over the time is almost always the highest. The reason for this may be the fact that both specialties (oral and maxillofacial surgery and general dentistry) involve more precision work than the other specialties.

Whether this ergonomic risk assessment of the individual specializations corresponds to the prevalence of WMSD cannot yet be concluded. In the literature, it is controversial whether the RULA values are directly linked to WMSD [ 37, 46, 47]. With regard to the prevalence of WMSD, most surveys show a differentiation between generalists and orthodontists; according to these, the WMSD prevalence is lower among orthodontists [ 12]. Although differentiated data have also been collected in a survey between Ds and DAs, details about the specialization direction were not probed [ 12]. The lifetime, 12-month and 7-day prevalence were greater among the DAs than among the Ds; this has been found to be true for the whole body as well as for the individual body regions [ 1, 4, 5]. Differentiated data per discipline would be interesting to explore, since in the specialty of orthodontics, followed by endodontology, the least work is performed (in percentage terms) at the highest ergonomic risk for the neck and trunk area. With regard to the orthodontic working method, these results can be explained by the fact that in the selected activities, the appliances are attached vestibularly, and so there is less need to lean forward and rotate than when working more palatally. This assumption should be explored more deeply in further analyses. WMSD prevalence in the previous 12 months in the neck and trunk region (85-48%) for DAs and (71-33%) for Ds [ 1, 4, 5] are also fundamentally higher in dentistry, per se, than in the German general population [ 48]. The prevalence for WMSD in Ds and DAs is also high for the wrists [ 49]; these are ergonomically very stressed in all specializations, as evidenced by the high RULA scores ( Figure 4; Table 3) due to the incessant fine motor movements that predominate here. However, comparative data for the general population are not available.

In the case of the activities analyzed in this study, it must also be borne in mind that these were selected from the spectrum of the respective specializations after consultation with specialist dentists and, therefore, only reflect a proportion of the possible dental treatment options. In addition, these treatments were performed on a dummy head and not on an actual patient, which may have influenced the results [ 6]. Furthermore, this study assumes that there are defined work patterns for the Ds and DAs in the different specializations; however, this does not necessarily reflect reality, as each team of practitioners has a distinct individual pattern of activities and procedures. Consequently, this study is a laboratory study and not a field analysis. The present study design was chosen so that the same conditions were available for each participant (per specialization) and, thus, comparability could be established. However, it must also be taken into account that the individual specialty-specific dental activities performed on the dummy head were not comparable with each other; this comparison was not the aim of the present analysis. Rather, it should be possible to produce a more detailed statement, on the one hand, as to how high the prevalence for WMSD is in Ds and DAs, and, on the other hand, whether these differ in the various specialist disciplines. The latter should demonstrate the versatility of dental treatment options and specify them by means of a kinematic analysis using an ergonomic risk analysis by RULA. However, the diversity of dental treatment options is less evident in the overall score and in the individual segments; for example, the relative average risk scores over the time vary minimally in the left and right upper and lower arms and the left and right wrist.

The comparison of Ds and DAs per specialization reveals isolated significant differences; although, no clear trends can be identified. Moreover, these absolute differences are also so small that they are likely to have little clinical relevance. This more detailed insight into the way of working may possibly be used for career starters with handicaps in order to advise them against a particularly burdensome specialization. However, this advice would then have to be given in consideration of the specific results for certain body regions. Nonetheless, in this way, there is the possibility that later occupational restrictions due to complaints in the musculoskeletal system could be less severe. Despite the fact that in the field of oral and maxillofacial surgery, the scores were sometimes higher than those of other specialties, all dental career starters should carry out systematic muscle building training, targeted at the weak points of the body, in order to counteract the static postures adopted with selected dental tasks.

In order to be able to represent dental activity in the best possible way, an activity protocol was developed. To ensure validity, the subjects were allowed to apply their individual working speed, analogous to daily patient treatment. Since median and relative risk distributions were determined in the evaluation of the kinematic data, the working speed had no influence on the results. One aspect that was not been considered in this study is the use of magnifying glasses. During dental treatment, these could positively favor the working posture since dental work is performed with indirect vision [ 50]. Since not all activities are performed using indirect vision and not all dentists work with it, the use of such means was not permitted in this study. It can, thus, be assumed that less time is spent in ergonomically stressful postures when working with indirect vision, particularly with regard to the trunk and neck. The torso would not have to be bent forward as far, while the neck and head would not have to be rotated or laterally inclined to such an extent. Working with a dental microscope, especially in oral surgery and endodontics, may also reduce working at such a high ergonomic risk score [ 51, 52, 53]. Regarding the ergonomic risk when working with indirect vision or a dental microscope, further analysis would need to be performed in the future.

Furthermore, it is also known that one and the same treatment in different quadrants causes a different posture [ 54]. Therefore, it would also be interesting to consider this aspect more closely in further analyses with regard to ergonomic risk and, in this context, to analyze the behavioral but also the relationship-related aspects that could positively favor the risk.

In principle, laboratory studies, such as the present investigation, have their limitations; nevertheless, the results of the entire SOPEZ project [ 4, 5, 6, 13, 31, 38, 41] provide important basic data for further investigations. Despite the measurements being made under laboratory conditions, it was, nonetheless, possible to demonstrate the risk potentials for the development and occurrence of WMSD, the high prevalence of which has already been documented in many surveys [ 1, 4, 5, 9, 55]. Future analyses should investigate the effect of parameters such as sex, age, weight, or height on body postures and ergonomics in dentists and dental assistants.

6. Conclusions

Within the framework of this quantitative, ergonomic risk assessment of selected dental tasks in the specialization fields of oral and maxillofacial surgery, endodontology, orthodontics, and general dentistry, it could be shown that the ergonomic risk in all dental disciplines reaches moderate to high ergonomic risk scores-for dentists and dental assistants. Nonetheless, minor differences can be observed, according to which the percentage of time spent working in the higher risk scores is lower for orthodontic and endodontic tasks, than for general dentistry or oral and maxillofacial surgery tasks. This is particularly evident in the neck, trunk, and wrist areas. The differences between dentists and dental assistants within a specialist discipline are only less existent.

Author Contributions

Conceptualization, W.B., C.E. and D.O.; methodology, F.H., L.F., W.B., C.E. and D.O.; software, F.H. and L.F.; formal analysis, F.H., L.F. and D.O.; investigation, F.H., L.F. and D.O.; resources, A.N., D.B. and D.A.G.; data curation, F.H., L.F. and C.M.-G.; writing-original draft preparation, F.H., L.F., W.B., C.E. and D.O.; writing-review and editing, E.M.W. and D.B.; visualization, F.H. and C.M.-G.; supervision, W.B., C.E. and D.O.; project administration, A.N., D.A.G. and D.O. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

The study was conducted in accordance with the Declaration of Helsinki, and approved by the ethics research committee of the Goethe-University (356/17; 7 February 2018).

Informed Consent Statement

All participants provided written informed consent to take part in the study in advance. This study was approved by the ethics research committee of the Goethe-University (356/17) in Frankfurt am Main, Germany. All subjects provided written informed consent.

Data Availability Statement

There are no further data or materials than shown in this manuscript.

Conflicts of Interest

All authors confirm that all methods were carried out in accordance with relevant guidelines and regulations. There is no competing interest in this article.

References

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2. Leggat, P.; Kedjarune, U.; Smith, D. Occupational Health Problems in Modern Dentistry: A Review. Ind. Health 2007, 45, 611-621. [Google Scholar] [CrossRef] [PubMed][Green Version]

3. Rafeemanesh, E.; Jafari, Z.; Kashani, F.O.; Rahimpour, F. A study on job postures and musculoskeletal illnesses in dentists. Int. J. Occup. Med. Environ. Health 2013, 26, 615-620. [Google Scholar] [CrossRef] [PubMed][Green Version]

4. La Rochelle, N.R. Work-Related Musculoskeletal Disorders among Dentists and Orthodontists. Master's Thesis, Virginia Commonwealth University, Richmond, VA, USA, 2017. [Google Scholar]

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Field of
Specialization

Occup.

Sex

Work Years

Age (Years)

Height (cm)

Weight (kg)

Oral and maxillofacial
surgeons

D

3 f/12 m

9.5 ± 9.0

36.3 ± 9.6

177.8 ± 8.2

75.5 ± 12.0

Task

Quadrant 1

Quadrant 2

Quadrant 3

Quadrant 4

1

D

Prepare tooth cavity with a cylindrical diamond bur and the use of wedges.

Occlusal reduction using an occlusal reducer.

Performing an entrance cavity and trepanation on tooth 36 using a diamond-coated cylinder.

Removal of supra- and subgingival tartar/calculus using scalers and
curettes.

1

DA

Suction during preparation of the cavity.

Suction during preparation and retracting the cheek with a
mirror if requested by the dentist.

Suction during preparation and retracting the cheek with a
mirror if requested by the dentist.

Suction during
curettage.

2

D

Create a Tofflemire die
using a die clamp.

Find the channel entrance using
an endo file.

2

DA

Activating and blending Ketac for the tooth filling
using a Ketac-set and mixing device and passing it to the dentist.

Suction during preparation and retracting the cheek with a
mirror if requested by the dentist.

Retracting the cheek with a
mirror if requested by the dentist.

3

D

Tooth filling with Ketac while using a Ketac-set, a
cougar/Heidemann and a ball-shaped plugger, followed by the removal of the Tofflemire clamp.

Manual preparation of the canal using an ISO
20-40 endo file with regular
irrigation using an irrigation cannula.

3

DA

No task.

Endodontology

Root canal
treatment of tooth 16

Root canal
treatment of tooth 26

Root canal
treatment of tooth 36

Root canal
treatment of tooth 46

2

D

3

D

Root canal
preparation with hand files at a
certain working length, irrigation after each file and removal of the rubber dam.

Root canal
preparation with hand files at a
certain working length, irrigation after each file and removal of the rubber dam.

Root canal
preparation with hand files at a
certain working length, irrigation after each file and removal of the rubber dam.

Root canal
preparation with hand files at a
certain working length, irrigation after each file and removal of the rubber dam.

3

DA

Setting the
working lengths of the ISO 35, 40, 45 files to 18 mm each and aspirating the rinsing liquid.

4

DA

Help with the
rubber dam
removal.

Help with the
rubber dam
removal.

Help with the
rubber dam
removal.

Help with the
rubber dam
removal.

2

DA

Assisting: coat brackets with
composite and
apply, cure with UV lamp.

Assisting: coat brackets with
composite and
apply, cure with UV lamp.

Assisting: coat brackets with composite and
apply, cure with UV lamp.

Assisting: coat brackets with composite and
apply, cure with UV lamp.

1

D

Palatinal and
marginal incision in regions 16 to 11.

Vestibular and marginal incision in regions 21 to 25.

Crestal incision in region 38 with a mesial relieving incision.

Crestal incision in regions 48 to 44.

2

D

Exposure of the palatinal impacted tooth 13 by
osteotomy using a surgical round bur.
If necessary, cut through the tooth using a
Lindemann bur.
Removal of the tooth 13 using a Bein root elevator or dental forceps.
Curettage of the dental sac.

Exposure of the vestibular
impacted tooth 23 by osteotomy
using a surgical round bur.
If necessary, cut through the tooth using a
Lindemann bur.
Removal of the tooth 23 using a Bein root elevator or dental forceps.
Curettage of the dental sac.

Exposure of the impacted tooth 48 by osteotomy using a surgical round bur.
If necessary,
cutting through the tooth using a Lindemann bur.
Removal of the tooth 48 using a Bein root elevator or dental forceps.
Curettage of the dental sac.

2

DA

Aspirating and holding of the flap with an instrument of choice, handing instruments as requested by the dentist.

Aspirating and holding of the flap with an
instrument of choice, handing instruments as requested by the dentist.

Aspirating and holding of the flap with an
instrument of choice, handing instruments as requested by the dentist.

Aspirating and holding of the flap with an
instrument of choice, handing instruments as requested by the dentist.

3

DA

Clamping the
needle in the needle holder and
cutting the seam with the scissors.

Clamping the
needle in the
needle holder and cutting the seam with the scissors.

Clamping the
needle in the
needle holder and cutting the seam with the scissors.

Clamping the
needle in the
needle holder and cutting the seam with the scissors.

RULA Score

Occupation

Oral and
Maxillofacial Surgery

Endodontology

General
Dentistry

Orthodontics

Median (IQD)

Rel. Av. RST

ERP (%)

Median (IQD)

Rel. Av. RST

ERP (%)

Median (IQD)

Rel. Av. RST

ERP (%)

Median (IQD)

Rel. Av. RST

ERP (%)

# data[].attributes.attachment_link.title
A RULA-Based Comparison of the Ergonomic Risk of Typical Working Procedures for Dentists and Dental Assistants of General Dentistry, Endodontology, Oral and Maxillofacial Surgery, and Orthodontics

# data[].attributes.attachment_link.description
Background: In general, the prevalence of work-related musculoskeletal disorders (WMSD) in dentistry is high, and dental assistants (DA) are even more affected than dentists (D). Furthermore, differentiations between the fields of dental specialization (e.g., general dentistry, endodontology, oral and maxillofacial surgery, or orthodontics) are rare.

# data[].attributes.attachment_link.title
Sci-Hub | Magnification loupes in dentistry: a qualitative study of dental studentsâ€™ perspectives | 10.1111/eje.12605

# data[].attributes.attachment_link.description
Wajngarten, Danielle; Botta, Ana Carolina; Garcia, PatrÃ­cia P.N.S. (2020). Magnification loupes in dentistry: a qualitative study of dental studentsâ€™ perspectives. European Journal of Dental Education, (), eje.12605-. doi:10.1111/eje.12605

# data[].attributes.attachment_link.readable_text
Abstract

Magnification devices improve direct and indirect vision and precision being significantly higher in microscope use compared to the loupes. Dental loupes are the most commonly used devices for magnification, due to the more affordable prices and the ease of use without major changes in the working protocol and ergonomics. Loupes primary benefits reported refers to ergonomics and posture, restoration evaluation/detection and overall treatment quality. There are some disadvantages that limit the use of loupes among dentists: lack of fixed position (fine movements of the dentist's head disturb the image of the magnified operating field); the need to change the loupes to achieve different magnification. On the contrary, the use of a dental microscope require minimum adjustment and effort so as to reduce postural deviation while working.

It has been more than 30 years since dental practitioners raised the issue of using dental operating microscopes (DOM) in restorative dentistry, identifying the benefits of magnification in diagnosis and treatment steps. The growth is evident in recent years, maybe because of the familiarity of dentists with dental microscopes which have already become implicit endowment for endodontic specialists. Fiber optic lighting is the key factor that complements the magnification offered by the microscope so that treatments can now be performed under increased safety conditions and in conditions of significantly higher quality than in the past.

Since the beginning of the 2000s the principles of minimally invasive dentistry have been widely promoted in dentistry. These principles are major impetus for the use of microscope by dentists. Working with magnification leads dentists to be more conservative with dental tissues.

Keywords: magnification, dental operating microscope, restorative dentistry, microscope restorations

The basic principles of restorative dentistry have not changed significantly in the last 30 years, but aesthetic, biological and mechanical criteria are now more strictly applied by dentists. Moreover, this tendency has been amplified by the quick evolution of the dental materials, equipment and techniques. Nowadays dentists do more aesthetic, biomimetic and predictable treatments that require less chair time with an increased success rate. These are difficult to be achieved without the use of magnification and also a good lighting. Since the 1970s, dentists have begun to consider the use of magnification in dentistry. Both microscopes and loupes have been widely adopted by dentists. Magnification can be divided in low-magnification (2x-8x), mid-magnification (8x-16x), and high-magnification (16x-25x). Microscopes provide adjustable magnification (magnification range 4x-25x), while most loupes provide fixed magnification (magnification range 2.5x-6x).

Magnification devices improve direct and indirect vision and precision being significantly higher in microscope use compared to the loupes [ 1]. Dental loupes are the most commonly used devices for magnification, due to the more affordable prices and the ease of use without major changes in the working protocol and ergonomics. They are available in multiple variants and models offering magnifications up to 6.5X, the most used being 2.5× [ 2].

The reported primary benefits of loupes refer to ergonomics and posture, restoration evaluation/detection and overall treatment quality [ 3]. There are some disadvantages that limit the use of loupes by dentists: lack of fixed position (fine movements of the dentist's head disturb the image of the magnified operating field); the need to change the loupes to achieve different magnification. On the contrary, the use of a dental microscope requires minimum adjustment and effort so as to reduce postural deviation while working.

It has been more than 30 years since dental practitioners raised the issue of using dental operating microscopes (DOM) in restorative dentistry, identifying the benefits of magnification in the diagnosis and treatment steps [ 4]. However, the effective widespread introduction of microscope use in restorative dentistry has evolved quite slowly. The growth is evident in recent years, maybe because of the familiarity of dentists with dental microscopes which have already become common tools for endodontic specialists [ 5]. Fiber optic lighting is the key factor that complements the magnification offered by the microscope so that treatments can now be performed under increased safety conditions and in conditions of significantly higher quality than in the past.

Since the beginning of the 2000s the principles of minimally invasive dentistry have been widely promoted in dentistry [ 6]. These principles represent major impetus for the use of microscope by dentists. Working with magnification leads dentists to be more conservative with dental tissues.

David Clark, founder of the Academy of Dental Microscopy and one of the pioneers of dental microscopy, said that "the greatest indicator of long-term retention of teeth is the volume of healthy natural dental tissue that remains after we finish treating a tooth" [ 7].

There are some mandatory requirements for using a dental microscope:

1. Working in indirect vision using a good dental mirror. The of maxillary and mandibular posterior teeth is impossible in direct view when the dentist is located between the 11:00 to the 12:30 position, for right-handed operators.

2. Using rubber-dam to prevent mirror fogging. Beside offering a good isolation, the rubber-dam keeps soft tissues retracted (tongue, lips) in order to have a wide working field.

3. Team work with a dental assistant to pass the instruments directly into the dentist's hand, as the dentist's eyes are fixed in the eyepiece and no longer able to reach for the instruments while working.

4. An up-mounted dental unit with all hand pieces situated above the patient's chest during treatment, which provides the assistant with access to change burs and rotary instruments and pass the air spray in low and high speed directly to the dentist.

5. Using of a dental chair with armrests. This allows the operator to have an important fixed point in the elbow in order to make fine and small amplitude movements. Chair should have important feature like adjustable height, width, tilt, backrest, seat pan and arm-rests.

6. Positioning the frequently used items close to the point of use (50-60 cm for most people) and not above or below waist height [ 8].

The benefits of DOM use in dentistry are now unanimously accepted:

1. Increased vision

Due to the magnification and transmitted light by fiber optics to the operating field, it is possible to treat more precisely because of improved visibility compared to the direct eye view [ 9].

2. Improve in overall quality of the treatment

It was proven that dentist do better restorative treatments under microscopic view due to the precision of the diagnosis and the proper completion of the treatment steps [ 10- 14]. A magnified image of the operative field may help the dentist to check cavity preparations, matrix fitting, saliva infiltration, remaining dentine debris, composite layering, occlusal morphology, macro/micro details, surface texture of restoration, air voids, impurities and over-contours in a better way.

3. Minimally invasive treatment with less dental hard tissue removal

The principles of minimally invasive dentistry have now become a priority for almost every dentist. It is easier to be achieved with magnification. Early detection of incipient enamel cavities before their expansion is impossible with the naked eye without magnification and the same is the removal of old filling materials with respect for the remaining healthy dental tissue.

4. Lesser time for the final occlusion check

Using the magnification in occlusal layering step, the operator may reduce the over-contoured resin material applied at the level of occlusal surfaces. Therefore that minimizes the occlusal adaptation time.

5. Ergonomic working position

Dental practitioners who use dental operating microscope declare the drastic decrease of the eye fatigue, musculoskeletal pains and the decrease of the psychological fatigue. This is because of the magnified image of the operating field, the increase of the lighting intensity, the ergonomic position during the work and the certainty of the control of the procedures performed. All these bring a net benefit of the dentist's quality of life [ 14- 18].

6. Comfort and motivation of the dentist

The use of a microscope increases the certainty of approaching certain treatments through the confidence of success brought by the possibility of controlling and verifying the details that are important in each treatment step, from cleaning and preparing the cavities to the finishing and polishing protocols.

7. Better communication with patient and dental assistant

The use of the dental operating microscope offers the possibility to take pictures and video data that can also be useful for the patient's motivation and information about his/her treatment plan. The data are meant to make the patient better and easier understand the explanations and may also be necessary for legal issues. Moreover, in 4-hands work, the nurse is more efficient if she/he can follow directly (either on the screen or through a dedicated eyepiece) the operating field as the dentist sees it. That allows the assistant to intervene promptly at certain stages where the aid is directly necessary (for adapting a matrix, fixing a dam clamp, etc.)

8. Avoid of iatrogenic damages

Working in a well-lit and around 20 times magnified operating field, gives the dentist the opportunity to be extremely precise in movements while using aggressive rotary instrumentation, especially burrs at high speeds. Thus, it is possible to avoid damaging the adjacent teeth during proximal cavity preparations, prosthetic crown preparations or to avoid deep dentin layer exposures leading to the opening of the pulp chamber, etc. These situations are, in many cases, difficult or impossible to control without a good magnification and effective lighting, especially when the operating field is visually obstructed by presence of cooling water mixed with enamel and dentin debris.

The benefits of magnification in restorative dentistry treatments are important in the following situations:

Gaps or impurities in restorative materials

Inspection of caries borders and remaining caries tissues

Evaluation of the marginal gaps of the restorations

Application of the liner for pulp protection selectively

Minimally invasive removal of amalgam restorations

Removal of excess composite materials

Adhesive excess removal [ 19]

Check if the composite is flowing into all aspects of the preparation, in al irregularities

Detect microscopic air bubbles in flowable composite, located either inside or on the external surface or margin of the flowable composite bolus [ 20]

Good finishing of margins [ 21]

Simplifying the finishing and polishing working protocol [ 22]

Improve the marginal integrity of proximal composite restorations [ 23].

There is a variety of additional upgrades for core microscope functions. Variable focal distance adapters have become available instead of fixed focal distances that limit the microscope to an object distance of 20-30 cm. These are often offered in top-of-the-line microscopes. Extendable (foldable) binoculars were introduced for improved ergonomics. A beamsplitter for a second eyepiece may be added in order to allow the assistant or another dentist/student to observe the operating field during the treatment. A beamsplitter for a photo/video camera allows the dentist to take photos and videos for the documentation of cases or for self-education of the dental team or students [ 24].

There are also a number of factors that limit the widespread use of microscope. The most important is the extremely high cost. However, there may also be problems like office space limitations or low motivation to use the microscope due to the lack of knowledge. Whatever the impediments, microscopy takes an increasing advantage for patients and dentists day by day.

The history of other medical specialties has already showed that new equipment may be hard to implement in daily practice. There is a fine balance between three major factors: the benefits to the treatment, the cost of acquisition and the effort made by the dentist for using it. In the case of microscopes, until now, only the first factor is unquestionable. Costs and reluctance to change will remain to be the major obstacles in spreading the use of microscopes in restorative dentistry for now.

References

3. Hayes MJ, BOH BHSc(Hons) MEd PhD, Rogers AA, BOH GDipPsych (Hons), Chuanon J, BOH BPharm GradCertPharmPrac, Tan T, BOH, Lai I, BOH, Yong E., BOH Dental and oral health students' perceptions of loupes. Int J Occup Saf Ergon. 2019:1-26. [[ PubMed] Google Scholar]

8. Jodalli PS, Kurana S, Shameema, Ragher M, Khed J, Prabhu V. Posturedontics: How does dentistry fit you? J Pharm Bioallied Sci. 2015;7(Suppl 2):S393-S397. [[ PMC free article] [ PubMed] Google Scholar]

Articles from Medicine and Pharmacy Reports are provided here courtesy of Universty of Medicine and Pharmacy of Cluj-Napoca, Romania

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The advantages of the dental operative microscope in restorative dentistry

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Magnification devices improve direct and indirect vision and precision being significantly higher in microscope use compared to the loupes. Dental loupes are the most commonly used devices for magnification, due to the more affordable prices and the ease of use without major changes in the working protocol and ergonomics.

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Dental Ergonomics to Combat MusculoskeletalDisorders: A Review

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Dental Ergonomics to Combat MusculoskeletalDisorders: A Review

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1. Definition

The term 'CAD/CAM' in dental technology is currently used as a synonym for prostheses produced by 'milling technology'. This is not entirely correct. CAD is the abbreviation for 'computer-aided design' and CAM stands for 'computer-aided manufacturing'. The term 'CAD/CAM' does not provide any information on the method of fabrication.

All CAD/CAM systems consist of three components:

1. A digitalisation tool/scanner that transforms geometry into digital data that can be processed by the computer

2. Software that processes data and, depending on the application, produces a data set for the product to be fabricated

3. A production technology that transforms the data set into the desired product.

2. CAD/CAM production concepts in dentistry

Depending on the location of the components of the CAD/CAM systems, in dentistry three different production concepts are available:

chairside production

laboratory production

centralised fabrication in a production centre.

a) Chairside production

All components of the CAD/CAM system are located in the dental surgery. Fabrication of dental restorations can thus take place at chairside without a laboratory procedure. The digitalisation instrument is an intra-oral camera, which replaces a conventional impression in most clinical situations. This saves time and offers the patient indirectly fabricated restorations at one appointment. At present, only the Cerec ® System (Sirona) offers this possibility. Other producers also plan to introduce chairside CAD/CAM systems to the market. Since the Cerec ® system functions with water-cooling, a variety of materials can be processed, from glass-ceramic to high performance oxide ceramic. Clinical observations on ceramic inlays are available over a period of 21 years. Scientific literature reported success rates for CAD/CAM produced inlays of 90% after ten years and 85% after 12 and 16 years. Historically, this system was the first CAD/CAM system in dentistry and is currently available in its third product generation. One of the benefits of this very mature system is the software that has been supplemented by a very exact three-dimensional reconstruction of the occlusal surface.

b) Laboratory production

This variant of production is the equivalent to the traditional working sequence between the dentist and the laboratory. The dentist sends the impression to the laboratory where a master cast is fabricated first. The remaining CAD/CAM production steps are carried out completely in the laboratory. With the assistance of a scanner, three-dimensional data are produced on the basis of the master die. These data are processed by means of dental design software. After the CAD-process the data will be sent to a special milling device that produces the real geometry in the dental laboratory. Finally the exact fit of the framework can be evaluated and, if necessary, corrected on the basis of the master cast. The ceramist carries out the veneering of the frameworks in a powder layering or overpressing technique.

c) Centralised production

The third option of computer-assisted production of dental prostheses is centralised production in a milling centre. In this variation, it is possible for 'satellite scanners' in the dental laboratory to be connected with a production centre via the Internet. Data sets produced in the dental laboratory are sent to the production centre for the restorations to be produced with a CAD/CAM device. Finally, the production centre sends the prosthesis to the responsible laboratory. Thus, production steps 1 and 2 take place in the dental laboratory, while the third step takes place in the centre. As a result, the configuration of the prosthesis remains in the hands of the dental technician. The benefit of outsourcing CAM production is to be found in the small investment requirement, since only the digitalisation tool and software have to be purchased, still having access to a high quality production process. In addition, this procedure results in greater independence, since there is no relation to a particular production technology (such as, eg milling technology). It must, however, be noted that presently almost all CAD/CAM systems are only available as closed systems. In other words, if one acquires a scanner from one manufacturer, this implies, in the case of a closed system, that there is only access to that manufacturer's processes and line of products. In addition, the dental laboratory loses the income from producing the framework, since it is fabricated in the production centre.

Many production centres also offer laboratories without a scanner the possibility of sending the master cast to the centre for scanning, designing and fabrication. The additional veneering of the frameworks for prosthetic restorations is carried out in the dental laboratory.

Recently, dentist's have been offered the possibility of sending the impression directly to the production centre (biodentis). This application is presently limited to ceramic inlays only.

An additional simplification in CAD/CAM production consists of intraoral data collection (optical impression). This means a digitalisation of what is now only an 'analogue' step in the production process. This could lead to additional improvement in quality and cost reduction. New software developments will make it possible to directly judge the quality of the preparation intraorally, before data are finally sent to the dental laboratory or production centre.

3. CAD/CAM components

3.1 Scanner

Under the term 'scanner' one understands, in the area of dentistry, data collection tools that measure three-dimensional jaw and tooth structures and transform them into digital data sets. Basically there are two different scanning possibilities:

optical scanners

mechanical scanners.

a) Optical scanners

The basis of this type of scanner is the collection of three-dimensional structures in a so-called 'triangulation procedure'. Here, the source of light (eg laser) and the receptor unit are in a definite angle in their relationship to one another. Through this angle the computer can calculate a three-dimensional data set from the image on the receptor unit. Either white light projections or a laser beam can serve as a source of illumination ( Fig. 1). The following can be named as examples of optical scanners on the dental market:

Lava Scan ST (3M ESPE, white light projections)

Everest Scan (KaVo, white light projections)

es1 (etkon, laser beam).

b) Mechanical scanner

In this scanner variant, the master cast is read mechanically line-by-line by means of a ruby ball and the three-dimensional structure measured. The Procera Scanner from Nobel Biocare (Göteborg) is the only example for mechanical scanners in dentistry. This type of scanner is distinguished by a high scanning accuracy, whereby the diameter of the ruby ball is set to the smallest grinder in the milling system, with the result that all data collected by the system can also be milled. The drawbacks of this data measurement technique are to be seen in the inordinately complicated mechanics, which make the apparatus very expensive with long processing times compared to optical systems.

3.2 Design software

Special software is provided by the manufacturers for the design of various kinds of dental restorations. With such software, crown and fixed partial dentures (FPD) frameworks can be constructed on the one hand ( Fig. 2); on the other hand, some systems also offer the opportunity to design full anatomical crowns, partial crowns, inlays, inlay retained FPDs, as well as adhesive FPDs and telescopic primary crowns. The software of CAD/CAM systems presently available on the market is being continuously improved. The latest construction possibilities are continuously available to the user by means of updates. The data of the construction can be stored in various data formats. The basis therefore is often standard transformation language (STL) data. Many manufacturers, however, use their own data formats, specific to that particular manufacturer, with the result that data of the construction programs are not compatible with each other.

The systems available on the market are differentiated mostly in their construction software. While many systems emphasise an indication spectrum that is as broad as possible, other manufacturers place emphasis on intuitive use and user-friendliness.

3.3 Processing devices

The construction data produced with the CAD software are converted into milling strips for the CAM-processing and finally loaded into the milling device. Processing devices are distinguished by means of the number of milling axes:

a) 3-axis milling devices

This type of milling device has degrees of movement in the three spatial directions. Thus, the mill path points are uniquely defined by the X -, Y -, and Z - values ( Fig. 3). The calculation investment is therefore minimal. A milling of subsections, axis divergences and convergences, however, is not possible. This demands a virtual blocking in such areas. All 3-axis devices used in the dental area can also turn the component by 180° in the course of processing the inside and the outside. The advantages of these milling devices are short milling times and simplified control by means of the three axes. As a result, such milling devices are usually less costly than those with a higher number of axes.

Examples of 3-axis devices: inLab (Sirona), Lava (3M ESPE), Cercon brain (DeguDent).

b) 4-axis milling devices

In addition to the three spatial axes, the tension bridge for the component can also be turned infinitely variably ( Fig. 3). As a result it is possible to adjust bridge constructions with a large vertical height displacement into the usual mould dimensions and thus save material and milling time.

Example: Zeno (Wieland-Imes).

c) 5-axis milling devices

With a 5-axis milling device there is also, in addition to the three spatial dimensions and the rotatable tension bridge (4th axis), the possibility of rotating the milling spindle (5th axis) ( Fig. 3). This enables the milling of complex geometries with subsections, as for example, lower jaw FPDs on converging abutment teeth (end molar tipped towards the medial plane) ( Fig. 4), or also crown and FPD substructures that, as a result of anatomically reduced formation, demonstrate converging areas in the exterior of the frame.

Example in the Laboratory Area: Everest Engine (KaVo).

Example in the Production Centre: HSC Milling Device (etkon).

The quality of the restoration does not necessarily increase with the number of processing axes. The quality results much more from the result of the digitalisation, data processing and production process.

4. Milling variants

a) Dry processing

Dry processing is applied mainly with respect to zirconium oxide blanks with a low degree of pre-sintering. This offers several benefits:

Minimal investment costs for the milling device

No moisture absorption by the die ZrO₂ mould, as a result of which there are no initial drying times for the ZrO₂ frame prior to sintering.

Disadvantages:

The lower degree of pre-sintering results in higher shrinkage values for the frameworks.

Some manufacturers also offer the option of milling resin material in a dry milling process [Zeno 4030 (Wieland-Imes), Lava Form and Cercon brain].

b) Wet milling

In this process the milling diamond or carbide cutter is protected by a spray of cool liquid against overheating of the milled material. This kind of processing is necessary for all metals and glass ceramic material in order to avoid damage through heat development. 'Wet' processing is recommended, if zirconium oxide ceramic with a higher degree of pre-sintering is employed for the milling process. A higher degree of pre-sintering results in a reduction of shrinkage factor and enables less sinter distortion.

Examples: Everest (KaVo), Zeno 8060 (Wieland-Imes), inLab (Sirona).

5. Materials for CAD/CAM processing

The list of various materials for processing by CAD/CAM devices depends on the respective production system. Some milling devices are specifically designed for the production ZrO ₂ frames, others cover the complete palette of materials from resins to glass ceramics and high performance ceramics. The following materials can normally be processed on dental CAD/CAM devices:

b) Resin materials

On the one hand, resin materials can be used for the milling of lost wax frames for casting technology; on the other hand, it is possible to use resin materials directly as crown and FPD frameworks for long-term provisional or for full anatomical long-term temporary prostheses ( Table 1). Prefabricated semi-individual polymer blanks (semi-finished) with a dentine enamel layer are provided by one manufacturer (artegral imCrown, Merz Dental). The exterior contour conforms to an anatomically complete anterior tooth crown, while the internal aspect of the crown is milled out of the internal volume of the blank.

c) Silica based ceramics

Grindable silica based ceramic blocks are offered by several CAD/CAM systems for the production of inlays, onlays, veneers, partial crowns and full crowns (fully anatomical, anatomically partially reduced) ( Table 2). In addition to monochromatic blocks, various manufacturers now offer blanks with multi-coloured layers [Vitablocs TriLuxe (Vita), IPS Empress CAD Multi (IvoclarVivadent)], for the purpose of full anatomical crowns. Due to their higher stability values, lithium disilicate ceramic blocks are particularly important in this group; they can be used for full anatomical anterior and posterior crowns, for copings in the anterior and posterior region and for three-unit FPD frameworks in the anterior region due to their high mechanical stability of 360 MPa. Glass ceramics are particularly well suited to chairside application as a result of their translucent characteristics, similar to that of natural tooth structure; they provide aesthetically pleasing results even without veneering. As a result of their relatively high portion of glass, these ceramics are, in contrast to oxide ceramics, etchable with hydrofluoric acid and thus can be inserted very well using adhesive systems.

d) Infiltration ceramics

Grindable blocks of infiltration ceramics are processed in porous, chalky condition and then infiltrated with lanthanum glass. All blanks for infiltration ceramics originate from the Vita In-Ceram system (Vita) and are offered in three variations:

Vita In-Ceram Alumina (Al₂O₃): suitable for crown copings in the anterior and posterior region, three-unit FPD frameworks in the anterior region

Vita In-Ceram Zirconia (70% Al₂O3, 30% ZrO₂): suitable for crown copings in the anterior and posterior region, three-unit FPD frameworks in the anterior and posterior region. Thanks to its superior masking ability this ceramic is suitable for discoloured abutment teeth

VITA In-Ceram Spinell (MgAl₂O₄): has the highest translucency of all oxide ceramics and is thus recommended for the production of highly aesthetic anterior crown copings, in particular on vital abutment teeth and in the case of young patients.

e) Oxide high performance ceramics

At present, aluminum oxide and zirconium oxide are offered as blocks for CAD/CAM technology.

This oxide high performance ceramic is ground in a pre-sintered phase and is then sintered at a temperature of 1520°C in the sintering furnace. Aluminium oxide is indicated in the case of crown copings in the anterior and posterior area, primary crowns and three-unit anterior FPD frameworks. The ground frames can be individually stained in several colours with Vita In-Ceram AL Coloring Liquid. Examples of grindable aluminum oxide blocks: In-Ceram AL Block (Vita), inCoris Al (Sirona) available in an ivory-like colour (Color F 0.7).

Yttrium stabilised zirconium oxide (ZrO₂, Y-TZP)

Zirconium dioxide is a high-performance oxide ceramic with excellent mechanical characteristics. Its high flexural strength and fracture toughness compared with other dental ceramics offer the possibility of using this material as framework material for crowns and FPDs, and, in appropriate indications, for individual implant abutments. The addition of three molecules of Y ₂O ₃ results in a stabilising tetragonal phase at room temperature, which, as a result of a transition to a monoclinic phase can prevent the progression of cracks in the ceramic (Transformation strengthening). Examples of Zirconium oxide blocks: Lava Frame (3M ESPE), Cercon Smart Ceramics (DeguDent), Everest ZS und ZH (KaVo), inCoris Zr (Sirona), In-Ceram YZ (Vita), zerion (etkon) and Zeno Zr (Wieland-Imes)

Processing can take place in different density stages

a) Green stage processing

Green stage: blank without heat treatment, ie an object pressed from ceramic powder and binding agents.

Since there was no pre-sintering, the object is as soft as chalk. This permits very easy processing, but results, due to the low degree of stability, in great problems in transport and application. Processing is by means of carbide metal grinders without liquid cooling. The green stage has an open porosity, and in firing a 25% linear shrinkage is to be expected. At present, zirconium oxide is not processed as a green stage in any of the CAD/CAM systems on the market.

b) White stage processing

White stage: pre-sintered blanks.

As a result of the thermal pre-treatment the organic compressing additives have vanished and the blank has an adequate stability. As a result of pre-sintering, the white body has already had shrinkage of approximately 5%. In the case of CAD/CAM production of objects from white bodies, the subsequent shrinkage of some 20% (linear) must be taken into consideration. Processing of white stage can be either with carbide metal grinders without water cooling or with diamond grinders with liquid cooling ( Fig. 5).

c) Processing in hot isostatic pressing condition

Some systems also process zirconium oxide in HIP (hot isostatic pressed) condition with diamond tools and water cooling. The advantages and disadvantages are as follows.

Advantages:

No sinter shrinkage, as a result no sinter distortions

No sinter furnace necessary

No additional time needed for sintering procedure.

Disadvantages:

Devices with high rigidity and stability necessary

Longer milling times, resulting in lower utilisation of devices

High wear of the cutters

No coloured blanks available on the market yet.

6. Future technologies

Generative production methods

Generative production methods are special CAD/CAM methods, which, in contrast to grinding technology, do not work by subtracting, but rather by adding material. In the dental area there are some areas of application for which this technology is already applied. In some production centres, so-called 'laser sintering devices' are used to produce crown and bridge frames from chrome cobalt alloys. Since the productivity of such devices is very high, dental restorations can be produced very cost-effectively. Basically, geometries are conceivable with this technology that cannot be realised with grinding technology.

7. Significance for the dentist

In recent years, the use of CAD/CAM technology has above all strongly influenced dental-technical production procedures. If one ignores chairside prostheses, the significance of this technology for the dentist is not immediately clear. In recent years, CAD/CAM production has clearly expanded the palette of materials for dental prostheses by providing access to new ceramic materials with high dependability. The stability values of zirconium oxide ceramics permit, in many areas of indication, the use of this material as an alternative to metal frames for permanent prostheses.

The production of long-term temporary prostheses has, as a result of the use of a virtual wax up on the computer, become faster, more convenient and more predictable. This method has already been implemented by computer-generated long-term temporary restorations, since it can be modified, by changing the form, to the functional and aesthetic satisfaction of the patient during a clinical test phase. The production of the definitive prosthesis should also be carried out by CAD/CAM technology and represents merely a copying process of the temporary prosthesis into the definitive prosthesis by a different material.

In spite of all the benefits of these new methods, the dentists working procedures will have to be adapted to the methods of CAD/CAM and milling technology. These include appropriate tooth preparations with the creation of a continuous preparation margin, which is clearly recognisable to the scanner, for example in the form of a chamfer preparation. Shoulderless preparations and parallel walls should be avoided. On the basis of present knowledge, a tapered angle of between 4° to 10° is recommended. Subsections and irregularities on the surface of the prepared tooth as well as the 'creation of troughs' with a reverse bevel preparation margin can be inadequately recognised by many scanners ( Fig. 6). In addition, sharp incisor and occlusal edges are to be rounded. Sharp and thinly extending edges as well as 90° shoulders in a ceramic restoration can result in a concentration of tension; in addition sharp edges cannot be milled exactly using rounded grinders in the milling device. The diameter of the smallest grinder is 1 mm in most systems, so structures smaller than 1 mm cannot be milled precisely. The result is an inaccurate fit.

A 360 degree shoulder or chamfer preparation is considered to be the appropriate marginal preparation geometries for CAD/CAM produced all-ceramic restorations. In the case of FPDs, the abutment teeth cannot show any divergence.

The precision of fit that can be achieved with the assistance of CAD/CAM systems is reported to be 10-50 m in the marginal area.8, 29, 32, 33, 34 Thus, the demands of the literature concerning marginal adaptation of dental restorations can be reached with this technology;35, 36 in addition, this production process achieves an industrial standard that does not have to deal with the variations of manually produced prostheses.23

8. Evaluation - advantages and disadvantages of computer-assisted production

CAD/CAM technologies have started a new age in dentistry. The quality of dental prostheses has improved significantly by means of standardised production processes. This makes very efficient quality management possible. On the one hand it increased the productivity tremendously and changed dental laboratories from manufacturers to modern computerised production centres. On the other hand this increase in productivity leads to a competitive capability to produce dental prostheses independent of the manufacturing site, which might be a major factor for the high wage countries to keep business volume in the country. Last but not least CAD/CAM technology has made it possible to machine interesting new materials like the high performance ceramics and titanium with high accuracy.

However, some drawbacks of this fabrication technology have to be mentioned. The high investment for machines might overextend the budget of smaller laboratories. Some applications are limited due to software and production procedures.

CAD/CAM technology has already changed dentistry and will replace more and more of the traditional techniques in fabricating dental restorations.

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Digital dentistry: an overview of recent developments for CAD/CAM generated restorations : Article : British Dental Journal

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The term 'CAD/CAM' in dental technology is currently used as a synonym for prostheses produced by 'milling technology'. This is not entirely correct. CAD is the abbreviation for 'computer-aided design' and CAM stands for 'computer-aided manufacturing'. The term 'CAD/CAM' does not provide any information on the method of fabrication.

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dental students knowledge of working postural requirements

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Reduce Seating Times With Digital Technology_ A Case Report

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Magnification in Dentistry_ How Ergonomic Features Impact Your Health

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Ergonomic Positioning_ A Few Degrees Add Years to Your Career

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Ergonomic Guidelines for Selecting Patient Chairs and Delivery Systems