Practicing Ergonomically Correct Dental Hygiene

Ergonomics is all about arranging the environment to fit the person working and living within it. Repetitive movement, such as scaling and root planing, may be detrimental to the physical as well as physiological condition of the dental hygienist. According to the United States Department of Labor, repetitive motion injuries resulted in the longest absences from work in 2002 with 23 days as the average number of missed work days.¹ The number of missed work days for repetitive motion injuries was higher than those for fires/explosions, transportation accidents, overexertion, slips, assaults, and exposure to harmful substances.¹

Clinical dental hygiene is physically challenging in a multitude of ways. Numerous musculoskeletal areas are vulnerable to injury as a result of instrumentation techniques, a combination of poor working postures, and the nature of the dental hygiene working environment.² Some signs and symptoms of musculoskeletal disorders can include weakness of muscles, numbness or tingling in muscles, pain, and a decrease in range of motion in extremities.¹ Choosing the best seating, lighting, and instruments for the individual dental hygienist’s work environment is key to reducing these types of injuries.

SEAT POSITIONING

The human body requires constant movement in order to reduce friction and maintain the overall health of joints and muscles. Dental hygienists routinely sit in the same position for extended periods of time during the workday while using repetitive motions throughout the body. Consequently, some risk factors cannot be completely eliminated while providing dental hygiene services. Dental hygienists accommodate each individual patient’s anatomy when providing treatment, which can make it difficult to locate and maintain ergonomically correct seat positioning. An ergonomic operator chair should consist of a stable leg base, lumbar support, and adjustable foot rests to encourage mobility and patient access. The operatory patient chair should be stable with movable arm rests and an adjustable head rest to support patient access and comfort.

Correct seat positioning begins with the operator’s feet flat on the floor. The seat of the operator chair should be at a 5°–10° angle toward the floor as this moves the pelvis toward a neutral seat position with a moderate lumbar curve and requires the least amount of effort within the muscles of the back. The chair height should also be adjusted so the hips are slightly higher than the knees. An operator chair that supports the dental hygienist and is properly adjusted helps maintain the desired low back curve.³

LIGHTING

Dental hygienists can improve vision and reduce fatigue by incorporating co-axial illumination or attached lighting devices (headlights) into their magnification system.² Headlights provide a source of light that is parallel to the dental hy – gienist’s line of sight.² Brighter light is not necessarily better. The ability to adjust the brightness for the individual user’s optimal level is helpful.²

The most common characteristics of headlights include:³

• Intensity and uniformity of the light source. The clinician should be able to control the intensity of the light emitted.
• Throughput of the fiber-optic cable. This measures the speed of information that is transferred through the cable.
• Portability and weight. Freedom of movement is essential while treating patients as is ensuring that the headlight is light enough for clinician comfort.²
• Color temperature and CRI (color rendering index). Color temperature describes the color of the light emitted by the light emitting diodes (LED). Choose a color temperature between 5500° and 6500° Kelvin. Lower color temperatures will have a yellowish light while higher temperatures will cast a bluer light. A temperature of 5500° Kelvin is equivalent to natural sunlight in color.⁵
• Battery life (LED only). Rechargeable batteries have a life expectancy of about 1 to 2 years. As the battery ages, it begins to hold less of a charge and results in a reduction in running time. Once the running time decreases to an unacceptable level, the battery needs to be replaced.
• Operator comfort. Vision enhancement headlights improve operator comfort by providing a lucid working viewpoint, reducing vision strain as well as improving posture.

The main advantage of headlights compared to conventional operating lights is the light source is parallel to the operator’s line of vision, thus eradicating shadows produced by hands, instruments, and patient positioning. Some advantages of LED headlights are improved portability, better color, less noise, less heat, lighter weight cord, and no burned-out bulbs. Some disadvantages include more diffuse light with a smaller central bright spot, decreased intensity with use, and the need to change batteries.⁶

INSTRUMENTS

Ergonomically designed dental instruments may assist in reducing the prevalence of musculoskeletal injury, as well as proprioceptive responses of the dental hygienist. Ergonomically designed dental instruments can be adjusted for control, adaptation, and the degree and distance of applied pressure.

A research study conducted by Dong et al⁷ demonstrates that instrument handle shape can affect hand muscle load and pinch force among dental practitioners performing a manual scaling task. The instrument with a round and tapered shape and a large diameter (10 mm) required the least force to use.⁷ When choosing instruments, the overall handle size, shape, weight, and maneuverability should be considered in order to reduce force exertion while maintaining neutral wrist positioning.

One option for modifying existing instruments to ergonomic instruments is through the use of gripping pads. The gripping pads enable the dental hygienist to use a lighter grasp, which results in diminished hand fatigue. These gripping pads aid in enlarging the handle diameter and decreasing pressure on the muscles of the hand and thumb, resulting in greater tactile sensitivity and effortless rotation of the instruments.

Other advancements in dental hygiene instruments include ultrasonic inserts and hand pieces equipped with a swivel feature. The swivel feature allows the clinician to change direction of the tip with greater ease and without interruption.

The implementation of ergonomic strategies should be developed to adhere to the needs of the dental hygienist rather than the dental hygienist adapting to the environment and equipment available. If successful, ergonomic interventions can help dental hygienists continue a long and comfortable career in practice.

REFERENCES

1. United States Department of Labor. Repetitive motion results in longest work absences. Available at: www.bls.gov/opub/ted/2004/mar/wk5/art02.htm. Accessed December 19, 2008.
2. Simmer-Beck M, Branson B. Minimizing work-related injuries in the dental office. Dimensions of Dental Hygiene. 2008;6(6 Spec Suppl):1-9.
3. Kolber EA. The musculoskeletal health of the dental worker. In: Murphy D. Ergonomics and the Dental Care Worker. Washington, DC: American Public Health Association. 1998;256-257.
4. Seltzer S. Vision enhancements in the operatory. Available at: www.dentaleconomics.com/articles/article_display.html?id=267062. Accessed December 19, 2008.
5. Molecular expressions. Science, Optics & You. Available at: http://micro.magnet.fsu.edu/optics/lightandcolor/colortemp.html. Accessed December 23, 2008.
6. LED Headlamps. Clinicians Report. Available at: www.cliniciansreport.org/book/led-headlamps. Accessed December 19, 2008.
7. Dong H, Loomer P, Barr A, LaRoche C, Young E, Rempel D. The effect of tool handle shape on hand muscle load and pinch force in a simulated dental scaling task. Appl Ergon. 2007;38:525-531.

From Dimensions of Dental Hygiene. January 2009; 7(1):22-23.