Instrumentation is one of the fundamentals of dental hygiene. However, the repetitive use of dental instruments presents ergonomic consequences that result from contributing factors, such as forceful exertions, repetition, the use of small-diameter handles, flexion and extension of wrists, pinch forces, static loading of the fingers and hands, awkward hand postures, and other prehensile (adapted for seizing or grasping) motions.1-3 Selecting the appropriate instruments and grasping them correctly can help dental hygienists maintain their health and prevent work-related musculoskeletal injuries.
SELECTION OF INSTRUMENTS
The selection of dental hygiene instruments and mirrors can be an overwhelming task. New instrument designs are complicated with multiple variations in color, diameter, weight, padding, and texture. Dental instruments vary widely from manufacturer to manufacturer and are not standardized by ergonomic guidelines.
Strategies to minimize the effect of the pinch grasp and to create a neutral posture include alternating instrument handle sizes, using instruments with larger diameter handles, using lightweight instruments, using instruments with rubber coating or padding, and using a variety of instruments throughout the appointment.2,4-8
The relationship of dental scaling instrument diameter and weight has been examined using surface electromyography (SEMG) and thumb pinch force among dental hygienists performing simulated scaling tasks. Studies revealed that both diameter and weight had significant effects on muscle activity and pinch force.8-10 Instruments with smaller diameters (7 mm) were associated with increased muscle activity and pinch force when compared to instruments with large diameters (10 mm). Handles larger than 10 mm had no additional benefits in reduction of muscle activity. Instrument weight did not impact muscle activity as significantly as diameter, however, lighter weight instruments overall tended to require less muscle activity and pinch force when performing simulated scaling tasks. The instrument with a large diameter (10 mm) and light weight (15 g) required the least amount of muscle activity and pinch force. Studies did not identify a weight limit that affects muscle activity, however, it is possible for instruments lighter than 15 g to require even less muscle activity and force. This concept needs further research.9
The relationship of mirror diameter, weight, and padding has been examined using SEMG among dental hygiene students performing simulated static mirror tasks.10 Results revealed padded mirror handles required less muscle activity in the thumb, and increased diameter and lighter weight required less muscle activity in the forearm. The study provided evidence to support the ergonomic value of using lightweight mirrors, lightweight mirrors with a larger diameter, and padded mirrors. The muscle activity response between the best and worst mirror handle for each muscle group was also examined, often revealing a mirror handle could be best for one muscle group and worst for a different muscle group. Alternating instrument handles throughout each appointment allows for varying muscles to work and rest throughout the appointment, which may improve musculoskeletal health.10
When selecting an instrument, dental hygienists should consider the design of the instrument and the desired function. For example, a wide diameter, lightweight, highly textured universal instrument may be the best selection when removing heavy deposit that requires a strong grip, whereas, a wide diameter, lightweight, padded area-specific instrument may be the best selection when light strokes are necessary for root planing. Within each setup dental hygienists should select multiple variations of instruments to best distribute work among all muscles10 and alternate instruments a minimum of two times per patient appointment.9
Another critical aspect of instrumentation is finger rest and finger rest position to support the fulcrum. Dental hygienists are taught that an effective, well-established finger rest is essential for stability, control, prevention of injury, patient comfort, and controlling the stroke. Finger rest selection should be based on convenience to area of instrumentation, ease of instrument adaptation, maintaining effective grasp, attaining correct angulations, stability of instrument, control of strokes, and clinician safety. The first choice for finger rest is the tooth adjacent to the tooth being treated.12 However, positioning such as this is not always feasible, and therefore alternative fulcrums such as opposite-arch, cross-arch, and extraoral are necessary.
The use of extraoral fulcrums is a controversial subject among dental hygiene educators. Proponents of the extraoral fulcrum agree intraoral fulcrums are adequate for supragingival and shallow subgingival instrumentation but argue that an extraoral fulcrum is essential for advanced periodontal instrumentation.13 Harold L. Meador, author and educator of the biocentric technique, believes neuromusculoskeletal pain is a result of violating the neutral position of joints and excessive use of a few small muscles. Meador endorses both internal and external finger rests to create neutral positions.14
Similar muscle activity is produced while scaling regardless of the fulcrum being used. Simulated scaling experiences demonstrate minimal ergonomic advantages in terms of fulcrums used and area of the mouth scaled.15 However, studies using SEMG and pressure sensors to examine the use of fulcrums revealed that using one or two finger rests, as compared to no finger rest, significantly reduced thumb pinch force and muscle activity.16 The evidence suggests that a stable finger rest is necessary to prevent muscle fatigue. However, the location of the finger rest should be based on access to targeted location and ease of use.
Dental hygienists are encouraged to assess the quality of their posture and the degree of hand pain by keeping a journal to record situations in the dental office that impact musculoskeletal pain. Additionally, sound evidence should be referenced before making any decisions or purchases to address ergonomic issues in the dental office. Scientific evidence supports the use of ergonomically designed dental instruments for the prevention of musculoskeletal disorders.
- Akesson I, Hansson GA, Balogh I, Moritz U, Skerfving S. Quantifying work load in neck, shoulders and wrists in female dentists. Int Arch Occup Environ Health. 1997;69:461-474.
- Horstman SW, Horstman BC, Horstman FS. Ergonomic risk factors associated with the practice of dental hygiene: a preliminary study. Prof Safety. 1997; 42: 49-53.
- Sanders MA, Turcotte CM. Strategies to reduce work-related musculoskeletal disorders in dental hygienists: two case studies. J Hand Ther. 2002;15:363-374.
- Michalak-Turcotte C. Controlling dental hygiene work-related musculoskeletal disorders: the ergonomic process. J Dent Hyg. 2000; 74:41-48.
- Liskiewicz ST, Kerschbaum WE. Cummulative trauma disorders: an ergonomic approach for prevention. J Dent Hyg. 1997;71:162-167.
- Stentz TL, Riley MW, Harn SA, Sposato RC, Stockstill J, Harn JA. Upper extremity altered sensations in dental hygienists. Int J Ind Ergon. 1994;13:107-112.
- van der Beek AJ, Frings-Dresen MH. Assessment of mechanical exposure in ergonomic epidemiology. Occup Environ Med. 1998;55:291-299.
- Dong H, Loomer P, Barr A, Laroche C, Young E, Rempel D. The effect of tool handle shape on muscle load and pinch force in a simulated scaling task. Appl Ergon. 2007;38:525-531.
- Dong H, Barr A, Loomer P, Laroche C, Young E, Rempel D. The effects of periodontal instrument handle design on hand muscle load and pinch force. J Am Dent Assoc. 2006;137:1123-1130.
- Simmer-Beck M, Bray KK, Branson B, Glaros A, Weeks J. Comparison of muscle activity associated with structural differences in dental hygiene mirrors. J Dent Hyg. 2006;80:8.
- Shenkar O, Mann J, Shevach A, Ever-Hadani P, Weiss P. Prevalence and risk factors of upper extremity cumulative trauma disorder in dental hygienists. Work. 1998;11:263-275.
- Wilkins EM. Clinical Practice of the Dental Hygienist. 9th ed. Philadelphia: Lippincott Williams & Wilkins; 2005:621-622.
- Pattison AM, Matsuda S, Pattison GL. Extra oral fulcrums—the essentials of using extraoral fulcrums for periodontal instrumentation. Dimensions of Dental Hygiene. 2004;2:20, 21-23.
- Meador H. The biocentric technique: a guide to avoiding occupational pain. J Dent Hyg. 1993;67:38-51.
- Cosaboom-Fitzsimons ME, Tolle SL, Darby M, Walker M. Effects of five different finger rest positions on arm muscle activity during scaling. J Dent Hyg. 2007;4:98.
- Dong H, Barr A, Loomer P, Rempel D. The effect of finger rest position on hand muscle load and pinch force in simulated dental hygiene work. J Dent Educ. 2005;69:453-460.
From Dimensions of Dental Hygiene. November 2009; 7(11): 46-48.