A demonstration of acceptable, compromised, and harmful operator posture as measured by Branson’s Posture Assessment Index from a frontal view.

THEhigh rate of musculoskeletal disorders (MSDs) reported by dental hygienists is no secret.^1-3 In 2001, 65% of registered dental hygienists reported having carpel tunnel syndrome (CTS) that required days away from work and 79% of dental hygienists reported days away from work due to repetitive motion exposure.⁴  The rate of MSDs among dental hygiene practitioners is higher than that of the general population.⁴ Despite these alarming numbers, dental hygiene educational programs continue to better prepare dental hygienists for needle stick prevention than for maintaining their musculoskeletal health.⁵

Work-related musculoskeletal disorders (WMSDs) result in a loss of income, increased medical expenses, rising workers’ compensation claims, and often require days off work, permanently decreasing the number of days worked or ultimately resulting in a career change. Proper education in ergonomics for the workplace can alleviate some of these problems.

The Development of CTS
The objective of ergonomics is to fit the physical workplace to the worker. This concept sounds quite simple, yet proves to be extremely complex. Experimental and epidemiological research acknowledges the origin of a WMSD as multifactorial.⁶ A conceptual framework (Figure 2) for developinga WMSD has been developed by the National Research Council. In this model, the work environment, organizational factors, and social context are influenced by physical and psychological factors and nonwork-related activities.

Click here for Figure 2

The development of CTS results from compression of the median nerve. The median nerve begins in the brachial plexus of the spine where the neck meets the shoulder. It runs the length of the arm next to the brachial artery through the carpal tunnel canal of the wrist and into the hand to supply feeling to the thumb, index finger, middlefinger, and half of the ring finger.⁷  Dental hygienists need to be conscious of the signs and symptoms of CTS.

Recent studies that analyzed the relationship between clinical CTS symptoms andnerve conduction tests concluded that the major symptom of CTS is pain at night,⁸ along with numbness and tingling. Minor symptoms of CTS are pain, weakness, and clumsiness.^9,10  The origin of hand pain maynot be in the hand and could possibly relate to other aspects of operator posture.

Dental hygienists are subject to manyrisk factors that increase the chance of developing WMSDs. The most significant nonmodifiablerisk factors include wrist-hand ratio and history of musculoskeletal disorderwithin the past 5 years.⁸  Others includefemale gender, age, the number of patients seen per day, body mass index, diabetes orother endocrine disorders, hypo or hyperthyroidism, pregnancy, obesity, andmenopause.^1,2,9,11 Modifiable risk factors,include activities, such as hobbies, that require repetitive use of the hands, the use of heavy pinch grip forces, non-neutral positions,awkward posture and positioning,localized pressure and use of repetitive motions, poorly fitted gloves, cold temperatures,vibrations, and work organization also significantly contribute to the developmentof CTS.^2,9,12,13

Sitting Posture
Maintaining a neutral posture while sitting may aid dental hygienists in the preventionof WMSDs and hand problems.^13,14  Dentalhygienists often work in the same positionfor long periods of time, performing tasks repeatedly, and bending or twisting the backin awkward positions.¹  Often there is a misconception that a simple change in instrument selection or wearing a splintat night will prevent CTS. These alterations are beneficial, however, due tothe interdependent nature of the many factors necessary to develop CTS,focus should not be limited to hands and arms alone.⁶  Dental hygienistsmust also consider the important role that sitting posture plays in physicalfactors related to MSDs.

An on-the-job assessment of posture is critical to determining posture weaknesses. In order to accomplish this assessment, dental hygienists needto understand the parameters of correct posture. Educational programs typicallyinstruct dental hygiene students on the ideal sitting posture.⁵  Thisinstruction includes holding the head, trunk, arms, and hips in neutral positions,typically at an angle of slightly less than 90°.¹⁵  This is often not practicalin the clinical setting and movement beyond the limits of neutral posture frequently occurs. However, the limits to which an operator can move beyond neutral are not well-established nor are they commonly recognized by clinicians.

Assessment
Practicing dental hygienists can use an assessment instrument to examine posture. This examination can be a self-assessment but is more ideally usedby a trained observer examining the clinician in real time. The Branson’sPosture Assessment Index (BPAI)16 is a validated instrument that calls foran observer to examine various posture check points and determine how farthe body part is angled off the 90° axis. The nature of dental treatment requires that the hygienist adopt postures in angulations away from neutral. WMSDs occur when the angulations are excessive or held for long periodsof time. Evaluation of these limits is important in understanding the levelsto which a clinician’s posture is harmful.

The BPAI (Figure 1) incorporates a grading scale for posture. The scale examines the clinician’s posture at three check points over a 5 minute time period and rates the overall posture as either acceptable, compromised,or harmful. The clinician’s hips, trunk, head/neck, shoulders, andwrists are evaluated. The final BPAI numerical score is a result of a mathematicalcalculation that multiplies values for each category at each timeinterval to determine a final sum. Posture scores that range from 10 to 40 are considered acceptable, scores ranging from 41 to 80 are compromised,and scores ranging from 81-194 are harmful. This instrument is designed tobe administered by trained evaluators during real-time observation.

Click here for Figure 1 - Branson's Posture Assessment Instrument (BPAI)

Observation
In the dental office, the assessment instrument is best used if several team members are familiar with the use of the evaluation system. Team memberscan take turns doing evaluations of each other. These evaluations should takeplace at different times throughout the work day. Other information needs tobe collected by the observer to thoroughly examine posture (Figure 3). For example, if the most compromised/harmful postures occur while sitting at the 10:00 position while using thin handled scalers on the buccal surfacesof the upper left quadrant, then the operator needs to make modificationswhile treating this area.

Click here for Figure 3

While real time observation is the most ideal method of evaluation, video taping may be an alternative method for self-observation. Applying the same self-assessment strategies mentioned above can be used when reviewing video tapes. The evaluator examines the posture of the individual using BPAI and also applies assessment principles. Some information may be lost in thevideo-taping but the dental hygienist can still make generalizations as to the weak areas in positioning and posture.

Intervention
Once posture weaknesses are identified, the hygienist needs to considerevidence-based interventions and ergonomic devices, such as loupes and ergonomically designed chairs and instruments, that will address the problem areas.

Magnification loupes are common devices used to prevent posture problems. The value of loupes is largely based on self-reports and focus groups; few studies exist to definitively outline the benefits. However, a recent study used video tape analysis to determine the effect magnification loupes had on operator posture of student dental hygienists. The study used trained observers and concluded that the posture of dental hygiene studentswas more acceptable when magnification loupes were worn thanwhen traditional safety glasses were used.¹⁸

Musculoskeletal disorders are caused by many factors and are experiencedby most dental hygienists at some point. Early ergonomics education and prevention are important in avoiding the negative impact of WMSDson a dental hygiene career. Dental hygienists need to be aware of compromised and harmful chair-side postures. Ergonomic devices such as magnification loupes have proven useful in keeping the head, neck, and trunk inless stressful postures. Dental hygienists should be on the alert for opportunities to self-assess and incorporate ergonomic strategies into the dental office environment.

Melanie Simmer-Beck, RDH, MS, has more than 11 years’ experience in clinical practice, both in general and periodontics. She is also assistant professor at the University of Missouri-Kansas City School of Dentistry and a member of the National Dental Hygiene Honor Society, Sigma Phi Alpha. Her research interests include ergonomics, advanced dental hygiene instrumentation, and infection control. She recently completed the first randomized controlled trial using surface EMG to evaluate muscle activity while pinch grasping dental mirrors.

Bonnie Branson, RDH, PhD, has been a dental hygiene educator since 1976, holding appointments at Southern Illinois University and Weber State University. She is currently associate professor at the University of Missouri-Kansas City School of Dentistry where her teaching and research interests include clinic instruction, public health, and ergonomic issues. She also practices one day per week in a general dental practice.

References

1. Anton D, Rosecrance J, Merlino L, Cook T. Prevalence of musculoskeletal symptoms andcarpal tunnel syndrome among dental hygienists. Am J Ind Med. 2002;42:248-257.
2. Lalumandier JA, McPhee SD. Prevalence and risk factors of hand problems andcarpal tunnel syndrome among dental hygienists. J Dent Hyg. 2001;75:130-134.
3. Akesson I, Hansson GA, Balogh I, Moritz U, Skerfving S. Quantifying work load inneck, shoulders and wrists in female dentists. Int Arch Occup Environ Health.997;69:461-474.
4. US Department of Labor. Special Report. Washington, DC: US Bureau of LaborStatistics; June 28, 2004.
5. Beach JC, DeBiase CB. Assessment of ergonomic education in dental hygiene curricula.J Dent Ed. 1998;62:421-425.
6. National Research Council. Work Related Musculoskeletal Disorders: A Review ofthe Evidence. Washington, DC: National Academy Press; 1998.
7. Interactive Hand Therapy Edition [CD-ROM]. Version 1.1. London: PrimalPictures; 2001.
8. You H, Simmons Z, Freivalds A, Kothari MJ, Naidu SH. Relationships between clinicalsymptom severity scales and nerve conduction measure in carpal tunnel syndrome.Muscle Nerve. 1999;22:497-501.
9. You H, Simmons Z, Freivalds A, Kothari MJ, Naidu S, Young R. The developmentof risk assessment models for carpal tunnel syndrome: a case-referent study.Ergonomics. 2004;47:688-709.
10. Bland JD. The value of the history in the diagnosis of carpal tunnel syndrome.J Hand Surg [BR]. 2000; 25:445-450.
11. Michalak-Turcotte C. Controlling dental hygiene work-related musculoskeletaldisorders: the ergonomic process. J Dent Hyg. 2000;74:41-48.
12. Keyserling WM. Workplace risk factors and occupational musculoskeletal disorders,Part 2: A review of biomechanical and psychophysical research on riskfactors associated with upper extremity disorders. AIHAJ. 2000;61:231-243.
13. Sanders MA, Turcotte CM. Strategies to reduce work-related musculoskeletaldisorders in dental hygienists: two case studies. J Hand Ther. 2002;15:363-374.
14. Meador HL. The biocentric technique: a guide to avoiding occupational pain. JDent Hyg. 1993;67:38-51.
15. Nield JS. Fundamentals of Periodontal Instrumentation and Advanced RootInstrumentation. 5th ed. Philadelphia: Lippincott Williams & Wilkins; 2004:14-21.
16. Branson BG, Williams KB, Bray KK, McIlnay SL, Dickey D. Validity and reliabilityof a dental operator posture assessment instrument (PAI). J Dent Hyg.2002;76:255-261.
17. Spielholz P, Silverstein B, Morgan M, Checkoway H, Kaufman J. Comparison ofself-report, video observation and direct measurement methods for upper extremitymusculoskeletal disorder physical risk factors. Ergonomics. 2001;44:588-613.
18. Branson BG, Bray KK, Gadbury-Amyot C, et al. Effect of magnification lenses onstudent operator posture. J Dental Educ. 2004;68:384-389.