Ergonomics in Dentistry–Designing Your Work

1. Introduction

In Greek, “ergo” means work and “nomos” means natural laws or systems. Ergonomics is an applied science concerned with designing products which are comfortable and provide safety (ADA). Ergonomics modifies wok to meet the needs of people, rather than forcing people to accommodate the work. The international ergonomic association defines ergonomics as, the scientific disciplines concerned with the understanding of interactions among humans and other elements of a system, and the profession that applies theory, principles, data and methods to design in order to optimize human wellbeing and overall system performance. (International Ergonomic Association http://www.iea.cc)

The term ergonomics was coined by British psychologist Hywelmurrel, at the 1949 meeting at the United Kingdom admiralty, which later led to the foundation of the ergonomic society.

2. Implications in Dentistry

Though the musculoskeletal disorders are common among medical professionals, it is more common among dentists and dental hygienists, because of prevalence of different postures in dental procedures, repeated work, prolonged stature, unsupported sitting and graping smaller and thin instruments for longer time (Alexopoulus, Staathi, & Charizani, 2004; Finsen, Christensen, & Bakke, 1998). Limited access during dental procedures is also known to be the one of the reasons for causing musculoskeletal disorders.

3. Goals of Ergonomics Include

• Prevention of work related musculoskeletal disorders and conditions which might lead to it

• Increasing safety and productivity

• Enhanced performance by eliminating unnecessary effort

• Improving the standard of care to the patient

4. Musculoskeletal Disorders in Dentistry

Literature suggests that the incidence of the musculoskeletal pain in dentists, dental hygienist & dental students range from 64 to 93% (Gross & Fuchs, 1990). The most common work related musculoskeletal disorders are low back pain, tendonitis, epicondylitis, bursitis, carpal tunnel syndrome. Cumulative Trauma Disorders (CTD’S) are health disorders arising from repeated biomechanical stress to the hands, wrist, elbows, shoulders, neck and back. Most common CTD’S are carpal tunnel syndrome and low back pain (Shugars, Miller, Williams, Fishburne & Srickland, 1987). Carpal tunnel syndrome has been associated with repetitive and forceful work (Liss, Jesin, Kusiak, & White, 1995).

Work related musculoskeletal disorders affect soft tissues of the body in areas like the neck, back, shoulders, elbow, hands, wrist, and fingers. Symptoms of work related musculoskeletal disorders may progress in stages from mild to severe.

Early Stage: aching and tiredness of the affected limb occur during the work shift but disappears at night and during day off work. No reduction and tiredness in work performance.

Intermediate Stage: aching and tiredness occurs early in the work shift & persists at night. Reduced capacity for repetitive work.

Late Stage: aching, fatigue and weakness persists at rest. Inability to sleep.

5. Application of Ergonomics in Dentistry

5.2 Guidelines to Prevent Work Related Musculoskeletal Disorders

5.2.1 Work Station

5.2.1.1 Workstation Layout

The Ergonomic Standard mandated by the Occupational Safety and Health Administration (OSHA) recommended that the most efficient and effective way to remedy “ergonomic hazards” causing musculoskeletal strain should be through engineering improvements in the workstation. (Liss, Jesin, Kusiak, & White, 1995; Gopikrishna, 2006).

Guidelines to be followed are:

• Instruments, medications, materials should be placed so that they are easily accessible to the dentists

• Easily adjustable chairs should be placed

• The temperature of the room should be checked

• Audio analgesia can be incorporated in the workplace

• The distance between the dental chairs should be sufficient enough so that the operators can move easily (Sanders & Michalak-Turcotte, 2004).

• Hoses should bepositioned away from the body

5.2.1.2 Operator Position

The main goal is to provide good access, support and mobility

• The operator stool should have a broad base pan

• Adjustable seat should be selected

• Seat should be adjusted so that the operator knee is slightly below the hip level and thighs are 100-110 degree to the trunk with feet resting flat on the floor

• Back rest height should be adjusted. The operator should sit back to take maximum lumbar support

• Foot rests should be adjusted

• Good hydraulic controls should be provided

• The distance between the working field and eye should be 35–40 cm

• The instrument tray should be positioned below the treatment point so that instrument can be picked only by moving the forearm

• Patient should be positioned so that the operator achieves neutral posture

• Elbow forearm angle is close to 90 degree

• Bending body forward to 10 degree at hip joint (Sanders & Michalak-Turcotte, 2004)

5.2.1.3 Patient Position

• Supine position of patient is usually the effective way by which operator achieves neutral posture

• Stability should be looked for

• Drop down arm rests

• Patient should be positioned in such a way that the patient’s mouth should be only slightly above the dentists elbow level

• There should be supplemental wrist/forearm support for operator

• Articulating head rests should be provided

• Hands free operation

• Swivel feature–allows chair to rotate in the operatory

• Large knobs should be eliminated as they, disturb the position of operator by hitting the dentalchair (Osuna, RDH, BS, & FAADH, 2006).

5.2.1.4 Rheostat Positioning

• Rheostat should be positioned so that the operator knee is about 90–100 degree angle (Alexopoulus, Staathi, & Charizani, 2004) (Figure 1).

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Figure 1.

Rheostat position.

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5.2.1.5 Light Illumination

• Main aim is to provide shadow free ,even operating field

• Light source placed directly above or slightly behind the patients head to provide ood illumination

• The intensity ratio between the dental operatory light and room lighting should be no greater than 3–4.6

5.2.1.6 Magnification

• It has been noted that the dentist posture is ergonomically better while using magnification lenses compared to their posture while using regular safety glasses

• Use of normal safety glasses necessitates 20 degree forward head bending which leads to flattening of low back curve; in contrast, use of magnification scope utilizes zero degree forward head bending, hence better results are provided

• Dentists should select the magnification that will support their position

• Factors considered include; working distance, depth of field, declination angle, convergence angle, magnification factor, lighting needs

There are three basic magnification systems available:

1. Single lens Loupes

2. Galilean Loupes

3. Prismatic Loupes

‘Magnification Continum’ is the term given to the growing number of magnification users (Sunnell, & Rucker, 2004) (Initially through naked eye progressing to the operating microscope).

5.2.1.7 Operating Microscopes

• The dental operating microscope is different from that of loupes in that it offers stereoscopic vision compared to loupes with its convergent vision

• The operating microscope has multiple levels of magnification from low(2.1, 3.2x)to high levels (13-19x)

• Shadow free lighting is provided

• Other advantages include–improvement in precision of treatment, communication with patient (through live video), improved ergonomics, and increase ease of documentation

Other newest technologies in the field of magnification include heads up display that involves a camera that is placed over patient and projects image to a monitor.

Other newer technological advances like CEREC helps the dentists to design and create all ceramic inlays, inlays, crowns, veneers for all teeth in one visit, by utilising digital impression technique there by eliminating the need for time consuming procedures.

6. Quadrant Dentistry

• Doctor time is maximized. Completing multiple restorations on one patient takes less time than doing the same number on multiple patients

• It minimizes cost. There is less paid in non–productive employee wages, fewer disposable goods, and less impression material, etc., which leads to huge savings

• It reduces office and doctor stress. Fewer patients equals less scheduling headaches, no–shows, and cancellations

• It increases the quality of care. Managing interproximal contacts, balancing aberrant occlusal forces, fine tuning occlusion, and delivering equally aesthetic restorations can be more predictably delivered in quadrants rather than one tooth at a time

• It increases revenue. Maximizing time, decreasing cost, less stress, and more dentistry significantly raises your bottom line

7. Scheduling

• Schedule Rest Breaks Between Patients

• Rotate Between Tasks

• Schedule Enough Time for Each Patient

• Switch Between Positions Throughout the Day

8. Training of Dental Personnel

The main goal of training dental personnel is to identify and avoid conditions which might lead to WMSD.

9. Stretches

Apart from different ways of practicing work, performing specific exercises for trunk, shoulder, hands, head and neck should be performed on regular basis to prevent these disorders (Nutalapati, Gaddipati, Chitta, Pinninti, & Boyapati, 2010).

10. Scope of Ergonomics

Advanced working techniques with magnification devices, visualization aids and dental equipment have all helped improve the ergonomics of working as a dental clinician (Hokwerda, 2008; Murphy, 1998). Awareness about the operating positions should be done to eliminate work related disorders. Four handed dentistry is ergonomically known to be the best way to reduce WMSD. Dentists’ knowledge and attitudes towards ergo-nomics should be improved and updated by educational programmes in order to increase awareness, reduce the incidence of occupational pathology and improve the quality of the dental health–care (Rundcrantz, 1991; Valachi & Valachi, 2003). Legal responsibility for protecting the health of dental personnel and patients should be stressed upon.

11. Conclusion

Though the reasons for work related musculoskeletal disorders are numerous among dentists, the main contributing factor is poor posture. Working ergonomically helps prevent work–related injuries. The clinician must optimize working environment to help eliminate awkward postures, physical wear and tear, and fatigue. By combining ergonomic magnification with postural strengthening, positioning techniques, working practices, chair side stretching, the multifactorial problem of work– related pain in dentistry can most effectively be addressed. Thus, successful application of ergonomics not only helps the dentists to improve their health, it also increases satisfaction as well as quality of work.