Introduction

Why is Ergonomics an Issue in Dentistry?

Ronald S. Mito, DDS, and Kallie Fernandez, BS

Copyright 2002 Journal of the California Dental Association.

There I was, a dentist in the prime of my career. I was driving my family to our annual summer vacation to Northern California when the first three digits of both hands started feeling profoundly numb. I thought it was driving fatigue resulting from the arms-up posture, so I would periodically lower my arms and shake my hands, and the numbness would dissipate. I would then alternate hands on the steering wheel. Yet, the numbness returned.

Then I started putting the picture together. During the previous few weeks, or was it months, I had begun to notice a very subtle but progressive onset of intermittent and sporadic paresthesias in the first few digits of my dominant hand, especially while holding a handpiece. Of course, at those times, I thought it was just excessive finger pressure; so I would take a brief break and rest my hand. I never appreciated the degree to which the situation was progressing, but the intensity was becoming so significant, I could no longer ignore it.

With both hands going numb, of course the usual mind speak occurred and I started to catastrophize, "Maybe you’ve got a C-spine problem with disc compression or something like that. It certainly can’t be carpal tunnel in both wrists at the same time. Anyway, I’m too muscular to have weak wrists." That quickly progressed to, "What if I have to have neck surgery? Am I willing to go through with it?"

The symptoms continued and dominated my thinking during the vacation. I realized I was numb while holding the telephone. A quart of milk slipped right through my fingers, even though I thought I was grasping it tightly. My anxiety level was starting to build.

As soon as I returned home, my primary care physician put me into a cervical collar; and we started the diagnostic process. Bottom line -- I had positive results on the "gold standard" tests for bilateral carpal tunnel. In a way, it was a relief that it wasn’t a C-spine problem, but it meant that I was facing bilateral wrist surgery and time away from practice; and I couldn’t do my administrative duties, i.e., computer work, either.

I am now nearly two years down the road, post bilateral carpal tunnel releases and doing quite well. I am certainly not 100 percent, but I am back to work and being cautious.

It was my personal experiences with repetitive motion, work-related musculoskeletal disorders that motivated me to dedicate an issue of the Journal of the California Dental Association to the topic of dental ergonomics.

As you may or may not know, the Occupational Safety and Health Administration created a federal ergonomics standard that was recently struck down by Congress. This was quite an onerous set of rules that would have dramatically affected many of us in every facet of practice. Over-regulation is a significant issue. However, the fact remains that work-related musculoskeletal disorders affect a significant portion of our profession.

According to OSHA, work-related musculoskeletal disorders occur when there is a mismatch between the physical requirements of the job and the physical capacity of the human body. Ergonomics, therefore, is the fitting of the job to the worker by designing the work and creating a work environment to help prevent work-related musculoskeletal disorders.¹ In the same publication, OSHA goes on to state that in 1996 more than 647,000 American workers experienced work-related serious injuries due to overexertion or repetitive motion, resulting in 34 percent of the lost work days due to injuries and costing an estimated $15 billion to $20 billion in direct costs and $45 billion to $60 billion in indirect costs in 1995.

What is the relationship between the practice of dentistry and work-related musculoskeletal disorders? In 1995, Mangharam and McGlothan conducted a review of the literature, nearly 60 papers, and published a summary of their findings in the book Ergonomics and the Dental Care Worker. According to their review, the literature supports the relationship between working as a dental professional and the incidence of work-related musculoskeletal disorders and psychological stress.² More recently, Hamann and colleagues published a study on the prevalence of carpal tunnel syndrome and median mononeuropathy among dentists. This study found that dentists reported hand and finger symptoms at a higher rate than the general population. However, when tested by electrodiagnostic criteria, the actual incidence of carpal tunnel syndrome was similar to that of the general population. What does this really mean? Hamann and colleagues state that the presence of symptoms increases the ultimate risk for carpal tunnel syndrome. Thus, the high rate of symptoms associated with dentistry supports the need for education regarding risk factors and early recognition of these symptoms to potentially enhance disease management.³

In 1997, Murphy published an article correlating the common risk factors in the general public to the practice of dentistry. These include constrained and fixed posture (sitting), awkward postures (neck/shoulder/wrist postures), exertion of force (extraction of teeth), repetitive motions (scaling), and duration of force (injection of anesthetic/scaling). Murphy also relates these risk factors to "ergonomic causes" -- work station design (operatory), tool design, work object (patient), work techniques, work organization (case load), and work environment (lighting).⁴

While the threat of regulatory intervention has been reduced for now, the prevalence of work-related musculoskeletal disorders in the dental workplace should generate concern among practitioners/employers to be knowledgeable and vigilant to protect themselves and their staffs. The purpose of this Journal issue is to provide the reader with current, useful information on work-related musculoskeletal disorders. The Laderas and Felsenfeld article provides a regulatory review and update. The Rucker study addresses the incidence and some of the background for work-related musculoskeletal disorders as related to postural and positional profiles of dentists. Jones and colleagues present contemporary diagnostic and treatment modalities for hand and wrist symptoms. Chang addresses the ergonomic impact of surgical telescopes and coaxial lighting. And lastly, Yoser presents preventive measures that we can all use on a daily basis.

Authors

Ronald S. Mito, DDS, FDS, RCS(Ed), contributing editor, is a professor and associate dean for clinical dental sciences at the University of California at Los Angeles School of Dentistry. He is also a member of the CDA Board of Trustees and a member of the ADA Council on Government Affairs.

Kallie Fernandez, BS, is a graduate of Loyola Marymount University and a pre-dental student.

References

1. Occupational Safety and Health Administration, Preventing Work-related musculoskeletal disorders. Ergonomic Fact Sheet, OSHA, Feb 1999.

2. Mangharam J, McGlothan J, Ergonomics and dentistry: a literature review. In, Murphy DC, ed, Ergonomics and the Dental Care Worker. American Public Health Association, Washington DC, 1998, p 25-75.

3. Hamann C, et al, Prevalence of carpal tunnel syndrome and median mononeuropathy among dentists. J Am Dent Assoc 132(2):163-70, 2001.

4. Murphy DC, Ergonomics and dentistry. NY State Dent J, 63(7):30-4, 1997.