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Trends in Ergonomics and Injury Prevention
A physical therapist/dentist team explain how to implement an injury prevention program through proper positioning, use of ergonomic equipment, chairside stretching, exercise, and more. PART 1
By Keith Valachi, DDS, and Bethany Valachi, MS, PT, CEAS
Although dentistry's basic mission of providing dental care to the public remains constant, the profession itself has experienced profound changes over the last several decades. Just as techniques and materials have adapted to new paradigms of practice, so, too, have methods of delivery of care evolved to address another consistent feature of the profession: work-related pain and musculoskeletal disorders (MSDs).
During the era of stand-up dentistry, dental practitioners commonly experienced low back and leg pain.1 To address this, and to increase efficiency, dentists began to sit in the 1960s, a technique that has evolved into the widely accepted four-handed, sit-down dentistry, using an array of ergonomic equipment. In spite of the many positive attributes of sitting, though, recent studies indicate that pain persists. However, the pain has now shifted to include the upper back, neck, shoulders, and wrists.2-5
So what potential injury problems still confront dental practitioners today? What is being done to address these issues, and in what direction are we headed? Before looking at the trends, it should be pointed out that the issue of work-related pain in dentistry is undeniably multifaceted.6-9 It may include factors that cannot be controlled, such as congenital predisposition, gender, environmental effects, operatory layout, and injuries outside the office. Many factors contributing to work-related pain, however, can be addressed by individual practitioners. These factors are the focus of this two-part feature on trends in dental ergonomics and injury prevention.
In this issue, Part 1 focuses on the proper use of equipment, including chairs, magnification systems, and handpieces, in dealing with dental-office injuries. It covers strategies to avoid poor positioning, gives tips for proper positioning, and offers advice on "What to look for" in ergonomic chairs.
In January 2003 DPR, Part 2 will cover trends in exercise and injury prevention, including strategies for dealing with prolonged, awkward posture and give examples of helpful in-office stretches.
Trends in dental equipment:
A wide variety of dental ergonomic equipment has been developed for dentistry, and many operators report positive effects after using it daily. Just possessing good equipment, though, does not assure getting the product's full ergonomic benefits. It has to be used properly, too. For example, when it comes to magnification systems, one expert cautions, "Properly selected and adjusted, surgical magnification can support balanced musculoskeletal ergonomics, but improperly selected or adjusted surgical magnification will support, or even create, poor working postures."10 With this advice in mind, here's a look at some of the ergonomic features of chairs, magnification systems, and handpieces.
Operator chairs. From an equipment standpoint, every practitioner's first line of defense is the operator chair. Many newer designs incorporate these three features:
1. Seat-pan tilt to facilitate proper spinal alignment and close positioning under a patient chair.
2. Lumbar support to help rest the lower back muscles and maintain the low back curve.
3. Arm supports to help reduce stress and fatigue in the upper back, neck, and shoulder muscles by providing an elbow fulcrum from which to operate. This, in turn, helps improve instrument stability. Supports may be unilateral or bilateral, including adjustable armrests that are fixed, swivel with the operator, or adjust via telescoping (forward and back) mechanisms.
Despite the availability of these helpful features, many operators still use chairs that are difficult to adjust. They do not realize the positive impact that a feature, such as a seat tilt, has on placing the spine in a safe and comfortable posture.11-14
Chairs that are difficult to adjust should be replaced or retrofitted.
Patient chairs. Chairs with wide, thick heads and backrests make it difficult for the operator to get close to the patient, encouraging awkward postures. Some newer patient chairs have narrow, thin heads and backrests, enabling the operator to position their legs more easily under the patient, gaining better visibility, while maintaining optimal posture.
Magnification systems. Poor visibility can cause the operator to bend forward at the neck, straining the discs, ligaments, and muscles of the cervical region. Over time, a prolonged, forward head position can lead to herniation (bulging) or degeneration of cervical discs.2,8
Many fine magnification systems are available. They offer two main benefits:
1. Scopes with at least 2X magnification will allow approximately the same "close-up" view achieved by hunching over the patient
2. Scopes with higher magnifications and optional lighting systems increase efficiency via enhanced visual detail and decreased shadowing of the field. These scopes also allow the operator to sit with optimal head and neck posture.
Specialists as well as GPs are incorporating surgical microscopes into their practices, which, by design, dictate improved postures.
Another new magnification device is a miniature dental endoscope, which allows for enhanced posture via its magnified, indirect, vision capabilities. It allows the operator to pass a miniature, lighted endoscope into a periodontal pocket. The operator then views a monitor as residual calculus is located on the root surface. The operator then re-enters the same location within the pocket with a scaler to efficiently remove the deposits. Use of this miniature endoscope reportedly allows non-surgical healing of chronic periodontal pockets.
Handpieces. Several newer handpiece designs can decrease hand strain. These include wide-diameter grip hand instruments, high-torque electric handpieces, rotary/sonic endodontic handpieces, and ultrasonic hygiene devices. All may relieve strain while increasing efficiency.9
Rubber dam. Even the lowly rubber dam has an unexpected positive aspect for dentist's musculoskeletal health. The dam automatically reflects lips, cheeks, and tongues, a job that typically is performed with the operator's mirror hand. The dam frees the mirror hand and allows for more frequent indirect (mirror) vision with proper posture.
Strategies to deal with poor positioning
Close proximity to a patient may be challenging to achieve. When an operator is unable to position a patient's head "in his or her lap," the operator must lean over to reach the patient, flexing forward from the mid-back to operate on the patient (see Fig 2). The operator's spine then literally must hang on muscles, ligaments, and discs, setting the stage for injury or MSDs.
Strategies for working in close proximity to a patient to facilitate proper posture include the following :
- Using a tilted chair seat, which allows an operator to position his or her knees under a patient headrest
- Using a patient chair with a narrow, thin, head- and backrest
- Using extendable headrests
- Straddling a patient.
One positioning mistake operators often make is "adjusting to the patient"-accommodating a patient's position rather than his or her own position. This can result in twisted, awkward postures for the dentist (see Fig. 3).
Oftentimes, "adjusting to the patient," can be avoided, as in the case of maxillary and mandibular procedures. For mandibular procedures, place the patient in a semi-supine position (Fig. 4). But, for maxillary procedures, take the time to position a patient in a true supine position-lying horizontally on the back (see Fig. 5).
During maxillary procedures, a neck roll may enable patients to maintain proper head position (see Fig 6). Also, simply asking the patient to turn his or her head can enable an operator to maintain optimal posture.
Using equipment properly, buying equipment with ergonomic features, paying attention to proper positioning, and learning about ergonomic principles all contribute to alleviating pain in dentistry. Stress management, flexibility, and exercise are also important, and trends in these areas will be covered in Part 2 in DPR's January 2003 issue.
Taking a holistic or multifunctional approach and focusing on the operator's physical and mental state is key to injury prevention in dentistry. And, in general, the trend in this field is moving toward the prevention of pain and injuries in dentistry before they occur, rather than waiting for a "painful episode." nDPR
References
1. Biller FE. Occupational hazards in dental practice. Oral Hygiene 1946;36:1994.
2. Rundcrantz B, Johnsson B, Moritz U. Occupational cervico-brachial disorders among dentists. Swedish Dental Journal 1991;15:105-115.
3. Lehto T, Helnius H, Alaranta H. Musculoskeletal symptoms of dentists assessed by a multidisciplinary approach. Community Dentistry and Oral Epidemiology 1991;19:38-44.
4. Marshall E, Duncombe L, et al. Musculoskeletal symptoms in New South Wales dentists. Australian Dental Journal 1997;42:240-246.
5. Chowanadisai S, Kukiattrakoon B, et al. Occupational health problems of dentists in Southern Thailand. International Dental Journal 2000;50:36-40.
6. Westgaard R. Effects of physical and mental stressors on muscle pain. Scandinavian Journal of Work and Environmental Health 1999;25:19-24.
7. Karwowski W, Marras W. The Occupational Ergonomics Handbook. Florida: CRC Press LLC; 1999:159,169-170,175,585–600,1134.
8. Cailliet R. Soft Tissue Pain and Disability. Philadelphia: F.A. Davis Co.; 1996:1-12, 35, 71, 124, 489-501.
9. Murphy D. Ergonomics and the Dental Care Worker. Washington, DC: American Public Health Association; 1998;113-128, 341-354, 360-362.
10. Rucker L. Ergonomics and the Dental Care Worker. American Public Health Association; Washington, DC 1998:192.
11. Callaghan J, McGill S. Low back joint loading and kinematics during standing and unsupported sitting. Ergonomics 2001:44:280-294.
12. Hedman T, Fernie G. Mechanical response of the lumbar spine to seated postural loads. Spine 1997:22:734-743.
13. Harrison D, Harrison S, Croft A. et al. Sitting biomechanics part 1: review of the literature. Journal of Manipulative and Physiological Therapeutics 1999;22(9):594-609.
14. Sjogaard G. Intramuscular changes during long-term contraction. In: The Ergonomics of WorkingPostures. Models, Methods and Cases. London and Philadelphia: Taylor & Francis Ltd. 1986:136-143.
Photo Credits
• Photos courtesy of Dr. Wayde Elliott's dental office and Dr. Keith Valachi's dental office.
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