INTRODUCTION
According to a 2010 study, women who sit more than 6 hours each day have approximately a 40% higher death rate and men a 20% higher death rate than those who sit less than 3 hours a day.¹ This is not good news for dentists, who tend to sit in excess of 6 hours during an average 8-hour day.²
The human body was designed for movement. Over thousands of years, the human body has depended on movement for its survival. But industrial and technological advances have done much to impede Mother Nature. With the onset of the Industrial Revolution, increasing numbers of workers performed relatively stationary tasks. With the advent of computers, the number of sedentary jobs has increased, as have the number of musculoskeletal disorders. One study showed the prevalence of low-back pain has increased by 2,700% from 1980 to 1993;³ a British study found that nearly one third of dentists who retire early are forced to, due to a disability;⁴ and numerous dental studies report that an average of 2 out of 3 dentists experience musculoskeletal pain.^5-16 It is reasonable to infer that changes in the way we use our bodies has contributed to this dramatic increase in work-related pain. In short, the body must move—and move properly—to stay healthy.
Since the introduction of seated (4-handed) dentistry, dentists tend to work for longer periods of time without taking a break, and they perform longer procedures.¹² Consider that when you sit in a static operating posture without leaning on your chair’s backrest, more than 50% of your body’s muscles must contract to hold the body motionless while resisting gravity. The static forces resulting from these prolonged, static postures (PSPs) are much more taxing on the body than dynamic (moving) forces.¹³
The resultant microtrauma from these PSPs include muscle imbalances, muscle ischemia, trigger points and spinal disc degeneration. This microtrauma develops through a series of events (Figure 1).

PROBLEMS ASSOCIATED WITH PROLONGED STATIC POSTURES
Muscle Imbalances
Even with the best ergonomic equipment, dentists frequently find themselves slightly leaning, usually more in one direction than the other. For example, most right-handed dentists tend to lean forward and to the right when they leave their neutral operating posture.¹⁷ Over time, the muscles can adaptively shorten on one side of the body, spine, or joint. This imbalance can exert asymmetrical forces, causing misalignment of the spinal column or in joints, with loss of range of motion in one direction over the other.¹⁸
Over time, the body’s musculature can adapt to the abnormal posture caused by these muscle imbalances and tend to maintain this unbalanced posture not only at work, but in leisure activities as well.

Muscle Ischemia
Maintaining static postures in dentistry requires sustained muscle contraction. When a muscle is contracted for a prolonged period of time, intramuscular pressure rises. This pressure compresses the blood vessels within the muscle, and during strong static contractions, can almost completely obstruct blood flow through the muscle.¹⁹ As lactic acid accumulates, muscular pain and fatigue result.^19-21 Even in the best working postures, dentists’ bodies perform static muscle work in the dental operatory.
Dynamic muscle work, on the other hand, creates a healthier environment for bodily repair. The rhythmic, pump-like contraction and relaxation of the muscles ensures adequate blood flow and oxygen to the muscles, as well as lactic acid removal.
Recovery time is relatively rapid after brief periods of high-level intensity muscle work, such as 20 minutes of uphill bicycling. However, recovery time from low-level muscle fatigue after working a 7- to 8-hour day (as in dentistry) is much longer. There is a risk that muscles may not even recover by the following workday. Human muscles are not designed for continuous, long-lasting contractions. They require rest periods to recover from even low-level exertion.²² It is a physiologic certainty that if the rate of tissue damage exceeds the rate of repair due to insufficient rest periods, muscle necrosis can result.

Trigger Points
Most dentists are already painfully familiar with trigger points. A trigger point is a group of muscle fibers that are in a constant state of contraction. They feel like a hard knot, nodule, or small pea. When pressed upon, they may be painful locally or refer pain to a distant part of the body. They neither allow the muscle to contract nor relax, thereby effectively decreasing flexibility and range of motion. Trigger points may be active (painful) or latent (causing stiffness and restricting range of motion).²³ Because they are caused by prolonged muscle ischemia, postural asymmetry and mental stress, it is easy to see why trigger points are so common among dental professionals.

Disc Degeneration
By adulthood, there is no blood supply to the inside of your spinal disc, and its only means of nutrition is via imbibition.²⁴ Think of the disc as a sponge. At rest, it absorbs no water; however, when compressed and released, it imbibes water. This is similar to the mechanism of the spinal disc. It requires alternate compression and relaxation to stay healthy. Sustained contractions in the muscles that extend your spine (as during active sitting) also reduce disc nutrition by compressing the discs, increasing intradiscal pressure.²⁵
Finally, lumbar disc pressures are generally higher when sitting than when standing. Compared to standing, lumbar disc pressures increase by 40% when you sit “actively” (without leaning on a backrest), and by 200% when sitting and leaning forward 40°.²⁶ This has particular relevance to dentistry, since dentists tend to sit for 78% of their working hours.²

PREVENTION THROUGH MOVEMENT
Movement is imperative in your operatory to decrease the structural damage from PSPs. You can incorporate the following movement strategies to help you move the workload from one group of muscles to another, prevent painful muscle ischemia, and reduce static spinal disc loading.

1. Change operating positions— Moving frequently between the 8 to 12 o’clock positions around the head of the patient is important; as you move around the patient’s head, the workload shifts slightly from one area in your body to another (Figures 2a to 2c). Your clock position will largely depend upon which position enables you a line of sight that is perpendicular to the occlusal surface.²⁷ The 12 o’clock position provides the most neutral, ergonomic operator posture, and should be utilized whenever possible. Note that when the patient chair is reclined, there should be at least 20″ of clearance between the headrest of the patient chair (when reclined) and counter.²⁸ If access in the 12 o’clock position is blocked, swivel the patient chair to improve access. A common ergonomic error among dentists is not positioning the patient properly when working on the upper arch, causing forward leaning and twisting. The occlusal plane of the upper arch should be up to 25° backward in relation to the vertical plane.^27,29 (For a full article on patient positioning, please read “Ergonomic Positioning: A Few Degrees Can Add Years to Your Career,” Dentistry Today, September 2010 available at dentistrytoday.com).
2. Switch stools—Research shows that regularly changing your seated posture can reduce low back pain.³⁰ Consider placing a traditional stool with armrests in one operatory, and a saddle-style stool in another (Figure 3). The saddle stool will place the dentist halfway between standing and sitting; this position uses different muscles than traditional seating, also decreasing spinal disc pressure.

Figure 3. The ideal sitting posture is one that changes. Try using one type of chair in one operatory and a different style in another.

Saddle stools have additional ergonomic benefits for the dentist. By placing the pelvis in a neutral position, the natural spinal curves are more easily maintained.³¹ Since they open the hip angle, saddle stools are ideal for gaining close proximity in the 9 o’clock position (especially helpful when working with wide patient chairs), and a good choice for dentists with short torsos who frequently find themselves working with elevated arms. The saddle stools allow for lower positioning of the patient and more relaxed arm and shoulder posture. They are also very easy to move around the patient’s head and great for confined operatory spaces. (For an in-depth article on operator ergonomic considerations when selecting operator stools, read the Dentistry Today September 2008 article, “Operator Stools: How Selection and Adjustment Impact Your Health” available at dentistrytoday.com.)
3. Moving seats—Studies show that seats that allow movement help prevent low-back pain and have positive ramifications for spinal health.³⁰ There are several styles on the market today. The new Virtu Dental Stool (Crown Seating) has dynamic movement technology that enables both the seat pan and backrest to follow the movement of the user. Brewer Design makes a dental stool with an air-filled bladder under the seat that may be inflated to allow varying degrees of movement. An air-filled, wedge-shaped seat cushion retrofits a nontilting operator stool and also offer the benefits of movement in the lumbar spine.³²

Figure 4. Alternating between standing and sitting has been shown to reduce lower back pain. Consider standing for extractions, injections, exams, denture adjustments, and impression-making.

4. Alternate between standing and sitting—One study reveals that dentists who alternate between standing and sitting have less low back pain than dentists who worked solely in a seated position.¹³ Dentists tend to spend more than three quarters of their total working hours seated, which places increased pressure on the lumbar discs.² Consider standing for extractions, exams, denture adjustments, injections and impression-making (Figure 4). You will need to ensure that your patient chair elevates to a height that enables a neutral standing posture when working. When standing, and especially for extractions, the mouth should be just below elbow level.

5. Reposition the feet—Contrary to what many dentists learned in dental school, the feet need not be statically placed in a tripod position throughout a procedure. The newest research in spinal biomechanics supports frequent repositioning during sitting.³⁰ Alternate between the following: both feet in tripod position, placing one foot (then the other), up on the stool pedestal, straddling the patient, or a runner-up position (one leg slightly down, behind and back). Shifting the rheostat from one foot to the other is also an effective way to move the muscle workload from one side of the low back to the other.
6. Chairside stretching—Research reveals that taking frequent breaks and moving are integral to an effective injury prevention program and pain control in dentistry (Figures 5 a to 5c).¹⁵

Frequent chairside stretching addresses every microtrauma that results from prolonged, static postures in dentistry: ischemia, trigger points, muscle imbalances, joint hypomobility, nerve compression, and disc degeneration.²⁸ The time commitment is minimal (only 10 to 20 seconds) and the benefits of stretching are numerous and include: increasing blood flow to muscles; increasing production of joint synovial fluid; reducing the formation of trigger points; maintaining normal joint range of motion; and increasing nutrient supply to spinal discs.
An effective chairside stretching program in dentistry targets those muscles and structures that are prone to ischemia and tightness. Not all stretches are appropriate for dental professionals.

Stretching During Microbreaks
It is important to know how to stretch safely (Sidebar). Chairside stretches should be performed every 45 to 60 minutes throughout the day²² and able to be performed easily at chairside while wearing gloves. Since men tend to be more prone to injuries related to tightness, it is especially imperative for male dentists to incorporate stretching into their daily regimen. Take advantage of 10 to 20 second microbreaks throughout the workday to stretch: while the assistant is light-curing or taking impressions, waiting for anesthetic to take effect, between patients, during a missed appointment, or during a recall exam.

CLOSING COMMENTS
Dentists know the importance of prevention, and you teach it to your patients on a daily basis. I challenge you to make a resolution in 2011 to implement movement prevention strategies to protect the significant investment you’ve made in your career and ensure a high quality of life, prevent disabling injuries and extend your career.

References

1. Patel AV, Bernstein L, Deka A, et al. Leisure time spent sitting in relation to total mortality in a prospective cohort of US adults. Am J Epidemiol. 2010;172:419-429.
2. Marklin RW, Cherney K. Working postures of dentists and dental hygienists. J Calif Dent Assoc. 2005;33:133-136.
3. Pope M. Muybridge lecture. In: Proceedings of the International Society of Biomechanics XIVth Congress. Paris, France. July 1993.
4. Burke FJ, Main JR, Freeman R. The practice of dentistry: an assessment of reasons for premature retirement. Br Dent J. 1997;182:250-254.
5. Akesson I, Schütz A, Horstmann V, et al. Musculoskeletal symptoms among dental personnel;-lack of association with mercury and selenium status, overweight and smoking. Swed Dent J. 2000;24:23-38.
6. Alexopoulos EC, Stathi IC, Charizani F. Prevalence of musculoskeletal disorders in dentists. BMC Musculoskelet Disord. 2004;5:16.
7. Augustson TE, Morken T. Musculoskeletal problems among dental health personnel. A survey of the public dental health services in Hordaland [in Norwegian]. Tidsskr Nor Laegeforen. 1996;116:2776-2780.
8. Chowanadisai S, Kukiattrakoon B, Yapong B, et al. Occupational health problems of dentists in southern Thailand. Int Dent J. 2000;50:36-40.
9. Fish DR, Morris-Allen DM. Musculoskeletal disorders in dentists. N Y State Dent J. 1998;64:44-48.
10. Finsen L, Christensen H, Bakke M. Musculoskeletal disorders among dentists and variation in dental work. Appl Ergon. 1998;29:119-125.
11. Lalumandier JA, McPhee SD, Parrott CB, et al. Musculoskeletal pain: prevalence, prevention, and differences among dental office personnel. Gen Dent. 2001;49:160-166.
12. Marshall ED, Duncombe LM, Robinson RQ, et al. Musculoskeletal symptoms in New South Wales dentists. Aust Dent J. 1997;42:240-246.
13. Ratzon NZ, Yaros T, Mizlik A, et al. Musculoskeletal symptoms among dentists in relation to work posture. Work. 2000;15:153-158.
14. Rucker LM, Sunell S. Ergonomic risk factors associated with clinical dentistry. J Calif Dent Assoc. 2002;30:139-148.
15. Rundcrantz BL, Johnsson B, Moritz U. Cervical pain and discomfort among dentists. Epidemiological, clinical and therapeutic aspects. Part 1. A survey of pain and discomfort. Swed Dent J. 1990;14:71-80.
16. Shugars D, Miller D, Williams D, et al. Musculoskeletal pain among general dentists. Gen Dent. 1987;35:272-276.
17. Kihara T. Dental care works and work-related complaints of dentists. Kurume Med J. 1995;42:251-257.
18. Saunders HD, Saunders RL, Kraus SL, et al. Evaluation, Treatment and Prevention of Musculoskeletal Disorders. Volume 1. The Spine. 3rd ed. Bloomington, MN: Educational Opportunities, A Saunders Group Company; 1993:47, 100-101.
19. Kroemer KHE, Grandjean E. Fitting the Task to the Human: A Textbook of Occupational Ergonomics. 5th ed. Philadelphia, PA: Taylor & Francis; 1997:8.
20. Kumar S. Biomechanics in Ergonomics. Philadelphia, PA: Taylor & Francis; 1999:12.
21. Cailliet R. Soft Tissue Pain and Disability. 3rd ed. Philadelphia, PA: FA Davis; 1996:71-72.
22. Sjogaard G and Jensen BR. Low-levels of Static Exertions. In: Marras WS and Karwowski W (Eds). Fundamentals and Assessment Tools for Occupational Ergonomics. Boca Raton, Fla: CRC Press; 2006:14-1-14-13.
23. Simons DG, Travell JG, Simons LS. Travell & Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. Volume 1. Upper Half of Body. 2nd ed. Baltimore, MD: Lippincott Williams & Wilkins; 1999:4,12,19,35,329-396.
24. Cailliet R. Low Back Pain Syndrome. 5th ed. Philadelphia, PA: FA Davis; 1995:10, 94-143, 279.
25. Ortengren R, Andersson GB, Nachemson AL. Studies of relationships between lumbar disc pressure, myoelectric back muscle activity, and intra-abdominal (intragastric) pressure. Spine (Phila Pa 1976). 1981;6:98-103.
26. Nachemson AL. Disc pressure measurements. Spine (Phila Pa 1976). 1981;6:93-97.
27. Hokwerda O, de Ruijter R, Shaw S. Adopting a healthy sitting working posture during patient treatment. optergo.com/uk/images/Adopting.pdf. Accessed February 18, 2011.
28. Valachi B. Practice Dentistry Pain-Free: Evidence-Based Strategies to Prevent Pain and Extend Your Career. Portland, OR: Posturedontics Press; 2008:102.
29. Murphy DC, ed. Ergonomics and the Dental Care Worker. Washington, DC: American Public Health Association; 1998:246-249, 306.
30. McGill S. Low Back Disorders: Evidence-Based Prevention and Rehabilitation. Champaign, IL: Human Kinetics; 2002:40, 51, 53-55,116, 175, 210-213.
31. Andersson GBJ, Chaffin DB, Martin BJ. Occupational Biomechanics. 3rd ed. New York, NY: Wiley; 1999:365-382.
32. FitBALL Wedge Ergonomic Cushion. posturedontics.com/fit_sit.php. Accessed February 18, 2011.

Ms. Valachi is a physical therapist, dental ergonomic consultant and CEO of Posturedontics, a company that provides research-based dental ergonomic education. She is a clinical instructor of ergonomics at OHSU School of Dentistry in Portland, Ore, and she lectures internationally at dental meetings, schools, and study clubs. She covers the above topics and much more in her book, Practice Dentistry Pain-Free: Evidence-based Strategies to Prevent Pain and Extend Your Career. She can be reached at (503) 291-5121, posturedontics.com, or via e-mail at bethany@posturedontics.com.

Disclosure: Ms. Valachi reports no disclosures.

Figure 1. Ask patients to scoot to the end of the headrest, then position with dental ergonomic cushions to properly support the spinal curves.

Figure 2. When treating the upper arch, the occlusal plane should be angled backward up to 25º in relation to the vertical plane. (Photo from Positioning for Success DVD, 2010.)

Seventy-five heads bowed reverently over their sim heads, diligently preparing a restoration on the distolingual of tooth No. 3. From the back, one would assume that the students were not wearing loupes, but from the side, a different reality became apparent. The students were working on the upper arch with the occlusal plane nearly vertical, causing excessive leaning and straining forward—even to see into the mirror. When the occlusal plane was tipped backward about 25°, the postural transformation was amazing.
This is one of the most common ergonomic mistakes I observe, not only in the schools, but also among dentists who have been in practice for many years—dentists who have the most expensive loupes, finest patient chairs, and state-of-the-art ergonomic operator stools. All of this is for naught if the patient isn’t properly positioned to preserve the dentist’s optimal working posture.
Not feeling any pain…yet? Are your patients’ teeth and periodontium completely healthy just because there is no pain? The progression to musculoskeletal disease (MSD) in dentistry is a slow, insidious process—and the proof is in the numbers:
An average of 2 out of 3 dental professionals experience occupational pain.^1-12
Nearly one third of dentists who retire early are forced to do so because of a MSD.¹³
In 2004, approximately $131 million in lost income was attributed to MSDs in the dental profession.¹⁴
The causes of MSDs in dentistry are multifactorial, ranging from nonergonomic loupes and improper selection of delivery systems, to generic exercise that worsens muscle imbalances. However, proper patient-positioning techniques can go a long way in preventing the progression toward chronic pain or potential injury for the operator. In fact, it has been shown that dentists who take the time to carefully position their patients to promote a direct view have significantly fewer headaches.¹⁰ Patient-positioning techniques will vary slightly depending upon the actual tooth surface being treated, the patient’s tolerance to reclining, and patient chair shape and width.
I had the honor of lecturing at the 2009 International Dental Ergonomics Congress in Krakow, Poland, and was privileged to be able to discuss the topic of patient positioning with the foremost dental ergonomists in Europe. Most dentists in Europe have traditionally positioned themselves quite differently than doctors in the United States, sitting primarily in the 9 o’clock position; which leads to slightly different MSDs than those reported in the United States (T. Dzieniakowski, Personal Communication, June 2009).¹⁵ Incorporating the key positioning concepts in the following ergonomic guidelines, I have measured greatly improved dentist and student postures. Many of these concepts are also becoming more widely accepted in Europe.

OPERATOR POSTURE
First, it is imperative that the dentist is seated properly and the stool is correctly adjusted.¹⁶ (See the Dentistry Today September 2008 article, “Operator stools: How Selection and Adjustment Impact Your Health,” available at dentistrytoday.com.) The assistant may be either standing or seated; alternating between these during the day can be very beneficial for the assistant’s musculoskeletal health. If seated, the assistant’s eye level must be 4 to 6 inches above the dentist’s for optimal viewing of the oral cavity. Some shorter assistants may require a taller cylinder on their stools to achieve this positioning.

Figures 3a and 3b. A dental cervical cushion can be used to facilitate proper positioning when treating the upper arch (3a) and reversed to treat the lower arch (3b). (Photo from Positioning for Success DVD, 2010.)

PATIENT POSITIONING SEQUENCE: UPPER ARCH
After the operator and assistant stools are properly adjusted, the patient must be positioned properly depending upon the quadrant and tooth surface being treated. For the upper arch, follow these general guidelines.
1. First, recline the patient to a fully supine position. This can be challenging for some patients who resist reclining due to postural hypotension, inner ear issues, vertigo, and a myriad of other conditions. However, this is oftentimes of a psychological origin. In these cases, try positioning the chair already partly reclined before the patient arrives. In this way, when the chair is fully reclined, it will not feel as dramatic to the patient. Another strategy is to meet them halfway—recline them slightly further than you actually need them reclined, then if they protest, say that you’ll meet them “halfway.” Placing a TV, mobiles, or other distractions on the ceiling can also go a long way in helping to get the patient more comfortable while supine.
2. Always ask the patient to scoot to the end of the headrest. This is especially important if using a flat headrest—reaching or leaning over the “dead” headrest space can lead to a myriad of musculoskeletal dysfunctions.¹⁴ Oftentimes, this is not done in deference to patient comfort—their spinal curves may not align properly with the patient chair support when scooted up all the way to the end of a headrest. This is easily resolved with dental ergonomic cushions that support the patient’s neck, lower back and knees (Figure 1).
3. Adjust the head tilt appropriately for the upper arch, angling the double articulating headrest up into the patient’s occiput. This will not only enable better viewing of the oral cavity, but also help relax the patient’s cervical muscles. The occlusal plane of the upper jaw should be tilted backward up to 25° in relation to the vertical plane.¹⁷ You can check for proper positioning from the side, using an instrument handle to visualize the angle of the occlusal plane (Figure 2). Cervical support cushions can greatly aid in attaining this position. Position the larger end under the neck for maxillary procedures and reverse the cushion for mandibular treatment (Figures 3a and 3b).
4. Adjust the height of the patient chair so the dentist’s forearms are parallel to the floor or sloping 10° upward. Another guideline is to position the occlusal surface at elbow level or slightly higher while operating.¹⁸ If positioning the patient above elbow level, armrests should be considered. The patient’s height may also be determined proprioceptively by closing the eyes and slowly moving the arms up and down until a comfortable working position is attained.¹⁹ Once the proper height is attained, position the patient chair accordingly.
5. Rotate and/or side-bend the patient’s head to view the treatment area. Rotation is best achieved with verbal cues, while side-bending can be performed manually. For example, when treating the occlusal of tooth No. 3, the patient’s head may be rotated slightly toward the operator.
The operator must then be positioned correctly depending upon the tooth surface being treated.
6. Move into a clock position that establishes a line of view that is perpendicular to the tooth surface being treated. This may be direct or indirect, depending upon the tooth surface being treated. Mirrors should be used whenever direct viewing of the oral cavity requires leaving neutral posture. One study revealed that more dentists who use a mirror are pain-free than those who do not utilize a mirror.²⁰

Figure 4. Lighting should parallel the operator’s line of sight as closely as possible to prevent shadowing. Overhead versus head-mounted light shown. Head-mounted lighting will cause the least shadowing. (Photo from Positioning for Success DVD, 2010.)

Figure 5. To enable a direct line of sight that is perpendicular to the lingual of No. 19, the operator moves to the 9 o’clock position.

Figure 6. The occlusal plane of the lower arch should be angled 30° to 40° above the horizontal plane when treating molars and premolars. (Photo from Positioning for Success DVD, 2010.)

For example, when treating the occlusal of tooth No. 3, the dentist should be in the 11 o’clock to 12 o’clock position to enable an indirect line of sight perpendicular to the tooth surface. In general, the 11 o’clock to 1 o’clock positions enable some of the most neutral operator postures, especially of the arms, and should be made easily accessible in the operatory.²¹ Frequent positioning at the 10 o’clock position without a mirror tends to encourage more arm abduction and neck/ shoulder problems.²⁰
7. Position the tray and delivery system within easy reach. Handpieces and instruments should be at about elbow level. Over-the-patient delivery systems should not cause upward reaching.
8. Identify nearby inter- or extraoral finger fulcrums that enable you to relax the hand and arm.
9. Direct the overhead light to prevent shadowing. The light should parallel the operator’s line of sight to within 15°. Thus, the light will be placed slightly behind and to one side of the operator’s head. A head-mounted light will parallel even more closely with the operator’s line of sight to prevent shadowing (Figure 4).20 Dr. Lance Rucker, professor and chairman of operative dentistry in the Department of Oral Health Sciences at the University of British Columbia, has done valuable research in this area. For the upper arch, a mirror may be used to reflect light onto the surface.
10. The assistant’s thighs should be angled toward the head of the patient, so assistant’s left hip is at patient’s left shoulder. The knees should preferably be interlocking with the dentist to gain the closest, safest positioning and posture.¹⁴ While this assistant positioning is a common practice in Europe, many dentists in the United States are uncomfortable with physically contacting the assistant’s leg.
The dentist may ask the assistant, “Can you see?”—a slight adjustment of the hand up or down on the mirror can greatly impact the assistant’s seat posture. The assistant may also need to adjust the stool position, depending upon the arch being treated—the stool may need to be slightly raised to visualize the lower arch. The assistant’s delivery system should be over the lap for easy retrieval of instruments/utilities.

PATIENT-POSITIONING SEQUENCE: LOWER ARCH
1. First, recline the patient to a semi-supine position. This will be only 20° elevated from the horizontal supine position. A common mistake is to position the patient halfway between supine and a full-upright posture for lower arch, which can make visualizing the oral cavity a postural challenge.
2. Adjust the headrest forward, so the patient’s chin tilts downward and the occlusal plane of the lower jaw is close to horizontal when the dentist is working in the 9 o’clock to 10 o’clock position. Reversing the position of a dental cushion will help in attaining this position (Figure 3b). The head will need to be tilted further back when treating anterior teeth of the lower jaw and further still when treating the lower molars and premolars.¹⁷
3. Adjust the height of the patient chair so forearms are parallel to the floor or sloping 10° upward. The height of the patient chair when treating the mandibular arch will need to be lower than when treating the maxillary arch. Some patient chairs do not adjust low enough for shorter dentists to attain a safe, relaxed arm posture in the semisupine position. A saddle stool can greatly aid in solving this problem, since it positions the dentist higher—halfway between standing and sitting.
4. Adjust the patient’s head position: Rotate the patient’s head to view the treatment area. For example, when treating the lingual of tooth No. 19, the patient’s head may be rotated away from the operator.
The operator must then be positioned correctly depending upon the tooth surface being treated.
5. Move into a clock position that establishes a line of view that is perpendicular to the lingual surface being treated. This may be direct or indirect, depending upon the tooth surface being treated. For the lingual of No. 19, the dentist should be in the 9 o’clock position to enable a direct line of sight perpendicular to the tooth surface (Figure 5).
When treating the anterior teeth, molars or premolars of the lower jaw, an 11 o’clock to 12 o’clock position may be used. For anterior lower teeth, the lower jaw should be angled backward about 30°. Tilt the headrest slightly backward or use the large end of the dental cushion to slightly elevate the chin. For molars and premolars, the lower jaw should be angled backward even further: about 40° (Figure 6).¹⁷ Professor Oene Hokwerda and colleagues have contributed greatly to this education in Europe. A more in-depth article on patient and operator positioning, “Adopting a Healthy Sitting Work Posture,” is available at esde.org.
6. Guidelines for positioning the tray, delivery system and lighting are similar to those for the upper arch.
When treating the lower arch, it is an excellent opportunity for a short- to medium-height assistant to stand. The assistant must stand very close to the patient to avoid leaning and reaching forward with the arms.

CONCLUSION
With tight patient schedules, emergencies, and production goals to consider, it is easy to overlook proper patient positioning. However, taking the time to position the patient, dentist, assistant, and equipment properly can not only have positive ramifications for the operator’s posture, comfort, and career longevity—it can also lead to better treatment and increased productivity.

Acknowledgement
The author wishes to thank Lee Lehman, manager of Henry Schein, Wilsonville, Ore, for the use of his beautiful showroom for photography, and to models Dr. Keith Valachi and Gayla Goodwin.

References

1. Akesson I, Schütz A, Horstmann V, et al. Musculoskeletal symptoms among dental personnel; lack of association with mercury and selenium status, overweight and smoking. Swed Dent J. 2000;24:23-38.
2. Alexopoulos EC, Stathi IC, Charizani F. Prevalence of musculoskeletal disorders in dentists. BMC Musculoskelet Disord. 2004;5:16.
3. Augustson TE, Morken T. Musculoskeletal problems among dental health personnel. A survey of the public dental health services in Hordaland [in Norwegian]. Tidsskr Nor Laegeforen. 1996;116:2776-2780.
4. Chowanadisai S, Kukiattrakoon B, Yapong B, et al. Occupational health problems of dentists in southern Thailand. Int Dent J. 2000;50:36-40.
5. Fish DR, Morris-Allen DM. Musculoskeletal disorders in dentists. NY State Dent J. 1998;64:44-48.
6. Finsen L, Christensen H, Bakke M. Musculoskeletal disorders among dentists and variation in dental work. Applied Ergonomics. 1998;29:119-125.
7. Lehto TU, Helenius HY, Alaranta HT. Musculoskeletal symptoms of dentists assessed by a multidisciplinary approach. Community Dent Oral Epidemiol. 1991;19:38-44.
8. Marshall ED, Duncombe LM, Robinson RQ, et al. Musculoskeletal symptoms in New South Wales dentists. Aust Dent J. 1997;42:240-246.
9. Ratzon NZ, Yaros T, Mizlik A, et al. Musculoskeletal symptoms among dentists in relation to work posture. Work. 2000;15:153-158.
10. Rundcrantz BL, Johnsson B, Moritz U. Cervical pain and discomfort among dentists. Epidemiological, clinical and therapeutic aspects. Part 1. A survey of pain and discomfort. Swed Dent J. 1990;14:71-80.
11. Rundcrantz BL, Johnsson B, Moritz U. Occupational cervico-brachial disorders among dentists. Analysis of ergonomics and locomotor functions. Swed Dent J. 1991;15:105-115.
12. Shugars D, Miller D, Williams D, et al. Musculoskeletal pain among general dentists. Gen Dent. 1987;35:272-276.
13. Burke FJ, Main JR, Freeman R. The practice of dentistry: an assessment of reasons for premature retirement. Br Dent J. 1997;182:250-254.
14. Valachi B. Practice Dentistry Pain-Free: Evidence-Based Strategies to Prevent Pain and Extend Your Career. Portland, Ore: Posturedontics Press; 2008.
15. Paszynska E. The Ergonomic and Health Status of Polish Dentists as Evaluated by a Questionnaire. Presented at: International Dental Ergonomics Congress; May 29, 2009; Krakow, Poland.
16. Valachi B. Operator stools: How selection and adjustment impact your health. Dent Today. 2008;27:148, 150-151.
17. Hokwerda O, de Ruijter R, Shaw S. Adopting a healthy sitting working posture during patient treatment. optergo.com/uk/images/Adopting.pdf. Accessed on March 13, 2010.
18. Chaffin DB, Andersson G, Martin BJ. Occupational Biomechanics. 3rd ed. New York, NY: Wiley InterScience; 1999:355-391.
19. Murphy DC, ed. Ergonomics and the Dental Care Worker. Washington, DC: American Public Health Association; 1998:294-295.
20. Rucker LM, Sunell S. Ergonomic risk factors associated with clinical dentistry. J Calif Dent Assoc. 2002;30:139-148.
21. Proteau R-A. Prevention of work-related musculoskeletal disorders (MSDs) in dental clinics. Montreal, Quebec, Canada: ASSTSAS. asstsas.qc.ca/_cms/plugins/recherche/view.aspx?xfileid=4846. Accessed March 13, 2010.

Ms. Valachi is a physical therapist, dental ergonomic consultant, and author of the book Practice Dentistry Pain-Free. This article is based on her new educational DVD entitled Positioning for Success in Dentistry. Dentists can earn 2 CE credits with the DVD, which also contains assistant and hygienist positioning techniques. The DVD as well as demo video clips are available at posturedontics.com. Ms. Valachi is CEO of Posturedontics, a company that provides research-based dental ergonomic education, and is clinical instructor of ergonomics at OHSU School of Dentistry in Portland, Ore. She is a member of the National Speakers Association, lectures internationally, and may be reached at bethany@posturedontics.com.

Disclosure: Ms. Valachi reports no conflicts of interest.

My previous articles on dental ergonomics published in Dentistry Today (September 2008, April 2009, and July 2009; these can be viewed at dentistrytoday.com) have focused on equipment in the operatory that can have a significant impact on the dentist’s musculoskeletal health. Along these lines, the obvious products that immediately come to most doctors’ minds are the operator stool, loupes, patient chair, and delivery system. However, there is a plethora of smaller, lesser-known products on the market today that can have just as positive an impact on your health as the more commonplace equipment. In this article on dental ergonomic products, we will delve into the smaller world of interventions. We’ll explore products with features that may, at first glance, appear simply interesting or unusual, but whose features offer powerful ergonomic benefits to help you work more comfortably, increase productivity, and extend your career.

Figure 1. The Feather Light (Ultralight Optics) is the lightest weight and smallest headlight on the market and delivers 39,000 lux.
Figure 2. The Isolite dryfield illuminator (Isolite) offers multiple ergonomic benefits by combining suction, illumination, and rubber dam in one product.
Figures 3a and 3b. The contoured shape of the dental headrest from Crescent Products allows for proper patient positioning for upper (3a; left) and lower (3b; right) arches.
Figure 4. The Physics Forceps (GoldenMisch) reduce 2 primary risk factors that lead to carpal tunnel syndrome.

LIGHTWEIGHT HEADLIGHTS
The most recent studies on overhead lighting recommend that the light closely parallel the operator’s line of sight to within 15° in order to prevent shadowing.^1,2 This means that the light will need to be placed behind and slightly to one side of your head. However, many lighting arms do not extend far enough for this positioning, and thus cast shadows over parts of the oral cavity.

RUBBER DAM AND LIP/CHEEK RETRACTORS
The ergonomic benefits of rubber dams and cheek retractors are often overlooked. The following excerpt is from the author’s book, Practice Dentistry Pain-Free: Evidence-based Strategies to Prevent Pain and Extend Your Career:

DRYFIELD ILLUMINATORS
One of the most innovative ergonomic products to appear on the scene combines the features of suction, illumination, and isolation into one convenient product. The Isolite dryfield illuminator (Isolite Systems) allows the practitioner to isolate quadrants of the mouth, retracting the tongue and cheek while propping the patient’s mouth open (Figure 2). Hands-free evacuation of debris and fluid occurs continuously while lighting is provided from within the mouth for shadow-free illumination. Additional ergonomic benefits include reducing the need to constantly reach overhead to readjust the light, it has no headlight, it frees up the assistant for other duties (since it retracts and suctions), it is easier and quicker to set up than a rubber dam, and there are no clamps to fall off. Productivity may therefore be positively impacted.

PATIENT POSITIONING AIDS
For optimal access and viewing, the occlusal plane of the upper arch should be angled backward about 20° (or so) from the vertical plane. Likewise, when treating the lower arch, the occlusal plane of the mandibular arch should be between 0° to 30° raised in relation to the horizontal plane.² Getting the patient into the proper position to preserve a safe working posture is often a challenge. A dental headrest cushion that is contoured to position for both upper and lower arches helps position the patient for better viewing (Figures 3a and 3b). Crescent Products also makes a larger Osteo Pillow for geriatric patients whose kyphotic head posture can be a challenge to support. Caution: Some dogbone-type headrests are too large for the patient’s cervical curve and actually push the head and chin forward and down. This is just the opposite of what you would want for viewing the upper arch.

GLOVES
Ambidextrous gloves may cause carpal tunnel syndrome-type pain, especially at the base of the thumb on the palmar side of the hand. Ambidextrous gloves are molded with the hand in a flat position and were originally designed for short medical exams.4 Then, dentists began using them for extended periods of time, finding that prolonged pulling of the glove into a working position caused strain in the thenar eminence, often resulting in pain. Fitted gloves are molded with the hand in a dynamic working position, and result in one third less force exertion than ambi-dextrous gloves.4

COMBINING TECHNOLOGIES: CARESCOPE
Traditional intraoral cameras often require wrist-twisting for proper placement and can be awkward to manipulate the focus. Combining the technology of an endoscope, lighted mirror, and an intraoral camera on one handpiece with a 360° swivel, the CareScope (CaringQuest) offers several ergonomic benefits during diagnosis. A magnified image is viewed on an LCD screen that allows the operator to sit upright. Meant to be held in the dentist’s or hygienist’s hand instead of a dental mirror, there is no need to interrupt treatment and get a camera. Offering 10x the magnification of loupes (5x to 40x), the CareScope may improve productivity with the im-proved visual acuity, and discovery of previously unnoticed caries and encourage better case acceptance through patient education on the LCD screen. When used in conjunction with the Isolite dryfield illuminator, the CareScope may also be used for restorative dentistry.

ATRAUMATIC EXTRACTION FORCEPS
Undoubtedly, extractions pose one of the highest ergonomic risks of the hand and wrist for general dentists. Combining a forceful grip with twisting, nonneutral postures of the wrist are 2 of the most potent risk factors for carpal tunnel syndrome.^5,6 A new extractor tool (Physics Forceps [GoldenMisch]) replaces strong grip force with leverage, dramatically decreasing muscle exertion and carpal tunnel compression (Figure 4). Properly placing the Physics Forceps for optimal leverage, the dentist then applies a light, constant, slow, rotational force on the forceps handle (do not squeeze the handle, which now functions as a lever) until the tooth releases. Not only are risk factors for carpal tunnel decreased, but the extraction time and stress for dentist and patient are also reduced.

SPINNING MIRROR
An ergonomic (and productivity) concern for both dentist and assistant are the postural, visual and time challenges of keeping the mirror clean and dry. Throughout the treatment, the assistant must constantly use air and water on the mirror to create a clear visual pathway. A Swiss microtechnology has produced a revolving dental mirror that self-cleans. The mirror spins at a rate that allows perfect clarity of vision while spinning away debris and spray without the interruption of the assistant cleaning the mirror. The mirror will also stop rotating immediately when soft tissue (tongue, cheek, etc) is touched. From a productivity standpoint, the mirror has much potential to reduce treatment time, and more fully utilize the assistant. The Everclear (Everclear I-DENT) dental mirror appears to be a revolution in the profession, is fully autoclavable, cordless and runs on rechargeable batteries.

INSTRUMENT DIAMETER AND WEIGHT
Instruments are available in a wide variety of diameters, ranging from about 5.6 mm to 11.5 mm. Larger instrument handle diameters reduce hand muscle load and pinch force. However, handle diameters greater than 10 mm (about three-eights inch) have been shown to have no additional advantage.⁷ When selecting instruments, try to include large diameters as well as other sizes, but avoid the very narrow diameter sizes (5.6 mm), which increase carpal tunnel pressure. Sleeves that fit over mirror handles and increase their diameter have been shown to reduce muscle load.⁸
Although instrument weight is not as significant a risk factor as handle diameter, lightweight instruments (15 grams or less) help reduce the muscle workload and pinch force.⁷

ARMREST OPTIONS
Simply the weight of your arm hanging at your side can be enough to cause neck and shoulder pain. Supporting this weight with armrests may actually reduce or eliminate neck/shoulder pain in some individuals.⁹ Here are 2 ways to quickly and economically add armrest support to your practice.

CLOSING COMMENTS
The proper selection and adjustment of ergonomic operatory equipment plays a key role in the management and prevention of work-related pain in dentistry. Dentists should seek out research-based, unbiased ergonomic product evaluations whenever possible prior to investing in new ergonomic dental equipment. While there are several excellent technical product reviews on the market, most reviews overlook important ergonomic features, which is why the author developed evidence-based, unbiased dental ergonomic product reviews that can be reviewed at posturedontics.com. However, equipment selection is just the tip of the iceberg when it comes to an effective dental ergonomics program. Research tells us this is a multifactorial problem that requires addressing numerous risk factors, including proper positioning of the patient, chairside stretching, proper body mechanics, as well as interventions outside the operatory to effectively prevent occupational pain in dentistry.

References

1. Murphy D, ed. Ergonomics and the Dental Care Worker. Washington, DC: American Public Health Association; 1998:246-249, 310-311.
2. Hokwerda O, Wouters JA, de Ruijter RA, et al. Ergonomic requirements for dental equipment. Guidelines and recommendations for designing, constructing and selecting dental equipment. Available at: optergo.com/images/Ergonomic_req_april2007.pdf. Accessed October 31, 2009.
3. Valachi B. Practice Dentistry Pain-Free: Evidence-Based Strategies to Prevent Pain and Extend Your Career. Portland, Ore: Posturedontics Press; 2008.
4. Powell BJ, Winkley GP, Brown JO, et al. Evaluating the fit of ambidextrous and fitted gloves: implications for hand discomfort. J Am Dent Assoc. 1994;125:1235-1242.
5. Phalen GS. The carpal-tunnel syndrome. Seventeen years’ experience in diagnosis and treatment of six hundred fifty-four hands. J Bone Joint Surg Am. 1966;48:211-228.
6. Mackin EJ, Callahan AD, Osterman AL, et al, eds. Rehabilitation of the Hand and Upper Extremity. 5th ed. St. Louis, Mo: Mosby; 2002:644-667.
7. Dong H, Barr A, Loomer P, et al. The effects of periodontal instrument handle design on hand muscle load and pinch force. J Am Dent Assoc. 2006;137:1123-1130.
8. Simmer-Beck M, Bray KK, Branson B, et al. Comparison of muscle activity associated with structural differences in dental hygiene mirrors. J Dent Hyg. 2006;80:8.
9. Travell JG, Simons DG, Simons LS. Travell and Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 1. Upper Half of Body. 2nd ed. Baltimore, Md: Lippincott Williams & Wilkins; 1999:278-307, 472-483, 491-503.
10. Rundcrantz BL, Johnsson B, Moritz U. Occupational cervico-brachial disorders among dentists. Analysis of ergonomics and locomotor functions. Swed Dent J. 1991;15:105-115.

Ms. Valachi is a physical therapist, dental ergonomic consultant, and author of the book Practice Dentistry Pain-Free: Evidence-Based Strategies to Prevent Pain and Extend Your Career. She is a clinical instructor of ergonomics at OHSU School of Dentistry in Portland, Ore, and she is a member of the National Speakers Association, lecturing internationally for dental meetings. For unbiased reviews of dental ergonomic products, free articles, and newsletters by Ms. Valachi, visit posturedontics.com. She can be reached at bethany@posturedontics.com. 

Disclosure: Ms. Valachi is CEO of Posturedontics, a company that provides research-based dental ergonomic education and evaluates dental ergonomic products.

MAGNIFICATION TYPES

Magnification designs have come a long way in the last decade. Lighter loupe designs with better declination angles have made believers out of many operators who previously purchased loupes, only to abandon them in frustration. As with any ergonomic product, magnification requires proper selection, adjustment, accommodation time, and usage to realize its benefits.
There are 3 basic types of magnification on the market today: the procedure scopes, surgical operating microscopes, and loupes (or telescopes).

Figure 1. Forward head posture is common with unmagnified vision, which can lead to a pattern of painful muscle imbalances (Posturedontics, 2008).	Figure 2. The procedure scope is the newest magnification aid and allows the operator to sit upright while viewing images on an LCD screen (MagnaVu procedure scope shown [Posturedontics, 2008]).

Figure 3. A microscope fitted with an ergonomic adapter (circled) enables a near-neutral head posture. (Global Surgical Microscope with Carr Binocular Extender shown, courtesy of Dr. Donato Napoletano.)

Loupes

Loupes, also referred to as telescopes, are the most popular type of magnification used in dentistry today. While none of these loupe systems provide neutral head posture (ear-over-shoulder), well-designed telescopes may significantly improve operator working postures in dentistry that contribute to musculoskeletal disorders2 and contribute to clinician comfort.1
Well-designed loupes should enable a working posture of less than 25° of forward head posture.11 Loupes range in strength from about 2x to 5x and are available in 2 basic styles: front lens mount (flip-ups) and fixed mounts, also called through- the-lens (TTL).
TTL loupes have the scope mounted directly into the carrier lens with a fixed declination angle. Since they are fixed, the loupes do not get knocked out of align­ment. Compared to flip-up loupes, they are lighter and offer a wider field of vision, since the scope is closer to the eyes. Prescription lenses can be included in the carrier lens of the fixed loupes to enable distance viewing. However, if the prescription changes, the loupes must then be modified by the manufacturer.
Flip-up loupes have the scope mounted on a hinge mechanism in front of the carrier lens and can be flipped-up during a procedure. Advantages, compared to fixed loupes, include a better declination angle for head posture and the ability to easily have eyeglass prescriptions changed by the clinician’s optician. On the other hand, flip-up loupes are sometimes heavier than fixed loupes and can also be knocked out of alignment.

ERGONOMIC CRITERIA FOR SCOPE SELECTION

Since poorly designed, or poorly adjusted loupes can cause or worsen pain syndromes, it is imperative that ergonomic guidelines are considered when selecting loupes. The 3 most important ergonomic factors to consider when purchasing loupes are: declination angle, working distance, and frame size/shape.

Figure 4. Loupes with a good declination angle (red lines) will allow the operator to work with minimal forward head posture. (Surgitel flip-up loupes shown [Posturedontics, 2008].)	Figure 5. A ratcheting hinge mechanism on the frame of a TTL loupe allows for significantly improved declination angle. (Designs for Vision loupes shown, courtesy of Dr. Kathleen Adams, OHSU School of Dentistry.)

Since glasses rest differently on each operator’s face, the same pair of loupes may have a slightly different declination angle from one person to the next. The declination angle (and resultant forward head posture) that various manufacturers offer varies dramatically (Table), and can either benefit or worsen your musculoskeletal health. Generally, flip-up style loupes allow for a steeper declination angle and more neutral head posture compared to TTL loupes. However, some manufacturers now offer a TTL loupe with a ratcheting mechanism on the frame that significantly im­proves the declination angle (Figure 5). When ordering TTL loupes, it is generally a good idea to request the steepest declination angle possible.

Working Distance

The working distance is defined as the distance from the eyes to the work­ing area. If the working distance is measured too short, it can result in excessive neck flexion or hunching.14 If possible, measure the working distance in your own operatory, with a patient in the chair. Sit in neutral operating position, with patient’s mouth at or 4 cm above elbow level. Have someone view you from the side and measure the distance from your eye to the work surface, or tooth. Working distances will vary for shorter operators (14 inches or less) to extra long working distances for very tall operators (more than 20 inches). Therefore, working distance should be tailored to the individual.

Figure 6. Large frames that sit low on the cheek allow lower positioning of scopes, leading to better head posture. (Orascoptic TTL loupes shown with Rudy Sports frame, courtesy of OHSU School of Dentistry student, Erich Ott [Posturedontics, 2008].)

SELECTING TELESCOPES

General guidelines for magnification strength are as follows: for hygienists, 2x to 2.5x; for general dentists, 2.5x to 3.5x; for endodontists/periodontists, 3.5× to 4.5× or higher. In general, operators should start with the lowest magnification at which they can view and control the surgical field. Keep in mind that higher-powered scopes will create a shorter depth of field, which may make working in multiple areas of the mouth difficult.

Illumination

Inadequate lighting can also lead to contorted postures to view shadowed areas of the mouth. To prevent shadowing, Dr. Lance Rucker, ergonomic expert and director of clinical simulation at University of British Columbia, advises positioning the operatory light parallel to, or within 15° of, the operator’s line of sight.15 This will usually require the operatory light to be located slightly behind the operator’s head, which may be difficult due to fixed ceiling track mounts.
Procedure and microscopes provide direct (parallel) lighting to the operator’s line of sight. Use of a headlight mounted to loupes will also closely parallel the operator’s line of sight. This can significantly reduce shadowing by aligning the direction of the light with your own sight line.
When properly utilized, magnification can significantly improve posture and therefore help prevent numerous musculoskeletal disorders to which dentists are prone. However, prolonged, static postures and weak postural muscles can still contribute to pain syndromes and MSD.16 By combining ergonomic magnification with chairside stretching, positioning techniques and postural strengthening, the multifactorial problem of work-related pain in dentistry can most effectively be addressed.

References

1. Spear FM. One clinician’s journey through the use of magnification in dentistry. Advanced Esthetics and Interdisciplinary Dentistry. 2006; 2:30-32.
2. Branson BG, Bray KK, Gadbury-Amyot C, et al. Effect of magnification lenses on student operator posture. J Dent Educ. 2004;68:384-389.
3. Ariens GA, Bongers PM, Douwes M, et al. Are neck flexion, neck rotation, and sitting at work risk factors for neck pain? Results of a prospective cohort study. Occup Environ Med. 2001; 58:200-207.
4. Marklin RW, Cherney K. Working postures of dentists and dental hygienists. J Calif Dent Assoc. 2005; 33:133-136.
5. Lehto TU, Helenius HY, Alaranta HT. Musculo­skeletal symptoms of dentists assessed by a multidisciplinary approach. Community Dent Oral Epidemiol. 1991;19:38-44.
6. Rundcrantz BL, Johnsson B, Moritz U. Cervical pain and discomfort among dentists. Epidemiological, clinical and therapeutic aspects. Part 1. A survey of pain and discomfort. Swed Dent J. 1990;14:71-80.
7. Hertling D, Kessler RM. Management of Common Musculoskeletal Dis­orders: Physical Therapy Princi­ples and Methods. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1996: 551-552.
8. Novak CB, Mackinnon SE. Repetitive use and static postures: a source of nerve compression and pain. J Hand Ther. 1997; 10:151-159.
9. Katevuo K, Aitasalo K, Lehtinen R, et al. Skeletal changes in dentists and farmers in Finland. Com­munity Dent Oral Epidemiol. 1985; 13:23-25.
10. Cuomo GM. Posture-directed vs. image-directed dentistry: ergonomic and economic advantages through dental microscope use. http://www. heryschein.com/usen/dental/services/cehp/HomeStudy.aspx. Published April 27, 2006. Accessed November 14, 2008.
11. Chang BJ. Ergonomic benefits of surgical telescope systems: selection guidelines. J Calif Dent Assoc. 2002;30:161-169.
12. Cailliet R. Neck and Arm Pain. 3rd ed. Philadelphia, PA: F.A. Davis; 1991:74-75.
13. Rucker LM, Beattie C, McGregor C, et al. Declination angle and its role in selecting surgical telescopes. J Am Dent Assoc. 1999; 130:1096-1100.
14. Valachi B. Vision quest: finding your best working distance when using loupes. Dental Practice Report. 2006;4:49-50.
15. Murphy DC, ed. Ergo­nomics and the Dental Care Worker. Washington, DC: American Public Health Association; 1998: 246-249, 310-311.
16. Valachi B, Valachi K. Mechanisms leading to musculoskeletal disorders in dentistry. J Am Dent Assoc. 2003;134:1344-1350.

Ms. Valachi is a physical therapist, dental ergonomic consultant and CEO of Posture­dontics, a company that provides research-based dental ergonomic education. Also a clinical instructor of ergonomics at OHSU School of Dentistry in Portland, Ore, she lectures internationally at dental meetings, schools, associations, and study clubs. She covers the above topics and much more in her new book, Practice Dentistry Pain-Free: Evidence-based Strategies to Prevent Pain and Extend Your Career, available through the Web site posturedontics.com or by calling (503) 291-5121. She welcomes comments and may be reached via e-mail at bethany@posturedontics.com.

Disclosure: Ms. Valachi is the CEO of Posturedontics and received no compensation for writing this article.

Historically, the importance of the dental operator stool has taken a backseat to the patient chair. Fortunately, this mindset is changing as new research is emerging on how various seating options impact a dentist’s musculoskeletal health. From an ergonomic standpoint, the operator stool is the most important chair in your treatment room. The ergonomic features on a stool and how you adjust them can profoundly influence your musculoskeletal health.
The operator stool should adjust to support your body in a neutral back, neck, and shoulder posture. With the wide variety of body sizes and heights among dental operators, certain stool types will fit you better than others. Tall and short operators, who are especially susceptible to pain syndromes due to ill-fitting seating, should be particularly conscientious when assessing special stool features, since these may benefit or worsen their musculoskeletal health.1 The following are basic features to evaluate when selecting traditional-type operator stools with a backrest and/or armrests (Figures 1a and 1b).

TRADITIONAL OPERATOR STOOLS

Figure 1a. An example of a basic stool with adjustable backrest and seat tilt (R04 Stool [Royal]).	Figure 1b. An example of an adjustable stool with fixed armrests and excellent lumbar support (Bodyguard Stool [Orascoptic]).

Hydraulic Controls

Nearly all operator stools today have hydraulic controls for easy, smooth adjustment of the stool. Fewer levers under the seat pan will usually make adjustment easier and quicker.

Tilting Seat Pan

When seated, your pelvis becomes the foundation of your posture. The more neutral your pelvic position, the more easily your spinal curves balance. This creates less strain in the back, neck, and shoulders. When seated on a flat seat pan with thighs parallel to the floor (as many dentists were taught in dental school), your pelvis rolls backward and the lumbar curve flattens.2,3 Flattening of the lumbar curve has detrimental effects on both the spinal musculature and discs.2,4,5
Research suggests that the most optimal seated posture for operators is hips higher than the knees, which requires a seat pan design that tilts slightly downward from back to front. This slight downward inclination of the seat pan (from 10° to 15°) helps facilitate the lumbar curve in the low back.6 This increases the hip angle to 105° to 125°, which results in a reduction of muscle activity and disc pressure in the lower back and may also enable a closer position to the patient for the operator.

Seat Contour

The seat contour greatly impacts comfort and support. The front edge of the seat should be padded and have a “waterfall” edge. This feature is especially important to reduce pressure on the posterior thigh’s blood vessels when sitting with your thighs sloping downward.

Seat Depth

Figure 2a. Seat pan depth should adequately support the operator’s thigh (Spirit Stool [Pelton & Crane]). (Figures 2a and 2b reprinted with permission from Valachi B. Practice Dentistry Pain-Free: Evidence-Based Strategies to Prevent Pain and Extend Your Career. Portland, Ore: Posturedontics Press; 2008.)	Figure 2b. Seat pans that are too deep for the operator may be temporarily modified by angling the backrest forward and retrofitting with a shorter cylinder.

As manufacturers recognize the growing number of women in the dental profession, more are offering short cylinder options and short seat pan depths to accommodate this population. Dental seat pans range from 14 to 18 inches deep and should support most of your thigh (Figure 2a). When seated all the way back on the seat and in contact with the backrest, the operator should be able to easily fit at least 3 finger widths behind the back of the knee without touching the seat. If the seat pan is too long, modifications should be made to accommodate the shorter dentist (Figure 2b).

Textured Seat

The seat’s material should be textured to prevent slipping when the seat is inclined forward. Materials such as leather are modern and sleek, but these and certain other synthetic types can be slippery, compromising much of the stool’s ergonomic benefits.

Backrest

A backrest with good lumbar support helps maintain the spinal curve when sitting.6 The lumbar support should be convex to support your low-back curve. It need only to be approximately 8 inches in height. This is an especially important feature with nontilting seat pans, which tend to flatten the low-back curve. Lumbar support helps preserve the lumbar curve, reducing muscle activity, disc pressure, as well as back and leg pain.3,7

Five-Caster Base on Rollers

Five casters are essential for safety. Wide wheelbases are more stable, but can be less maneuverable and prevent close positioning to the patient if they hit the patient chair base. Make sure the roller-type is appropriate for your operatory floor (carpet versus hard floor). The wrong rollers can make it difficult to move the chair around the patient.

Armrests

Studies support the use of armrests in the prevention of neck, back, and shoulder pain.8-10 These are especially important for endodontists and dentists who are forced to reach forward with the arms more than 15° due to a protruding abdomen (ie, pregnancy) or a large chest. Armrests should be highly adjustable to provide support to the operator in a neutral working posture. Designs vary widely from fixed-adjustable armrests (Figure 1b) to swiveling and telescoping armrests, which move with the operator. Proper height adjustment of the armrest is essential, since adjusting the armrest too high or too low can lead to a worsening of neck and shoulder pain. Likewise, positioning the armrests too far forward can encourage the operator to lean forward, thus compromising operator posture.

Cylinder Height

The height of the stool cylinder can significantly impact your seated posture and musculoskeletal health. Stools are sometimes sold with a standard height cylinder with little regard to height of individual operators. There is no height standardization for dental stool cylinders. Dental stools marketed as average, medium, standard, or “regular” height may vary widely in adjustability. The adjustments can be found from a low of 13 inches to a high of 30 inches. A “medium” height cylinder from one manufacturer may be called “short” by another manufacturer. In general, it is recommended that a “short” operator have a stool with height adjustment from 16 to 21 inches, and taller operators from 21 to 26 inches.11 Retrofitting a stool with a short or tall cylinder may allow you to better maximize the ergonomic benefits of your stool.1

Saddle-Style Stools

Figure 3. The saddle stool places the pelvis in a near-neutral position, thus naturally balancing the spinal curves. (Figures 3 and 4 reprinted with permission from Valachi B. Practice Dentistry Pain-Free: Evidence-Based Strategies to Prevent Pain and Extend Your Career. Portland, Ore: Posturedontics Press; 2008.)

When you are sitting in a horse saddle, your pelvis is in a near-neutral position, as in standing posture (Figure 3). This pelvic position allows your spinal curves to balance more easily in proper alignment and reduces muscle strain.12 This is why backrests are considered optional on saddle stools. By design, saddle stools will place more compression on the peritoneal area and should be carefully evaluated for suitability to the operator. Saddle stools have additional benefits: they are great for confined areas due to their very low profile; allow close proximity to patient chairs with thick upper backrests by opening the hip angle; easier to maintain your natural spinal curves when leaning forward; are helpful for tall dentists with low-back pain, since they decrease low-back strain; and they prevent lifting the arms/shoulders in shorter dentists, since they allow for a lower positioning of the patient.

Figure 4. Bodyguard Stool Operator Stool Adjustment To attain a balanced seated posture, follow these adjustment steps: Adjust the backrest height so the most convex portion nestles in your low-back curve. Move the backrest away from your back. Sit all the way back on the seat. Place 3 fingers behind your knee. The finger closest to the seat should not touch the seat pan. Tilt the seat slightly forward (only 5° to 15°). Adjust the height with feet flat on the floor, so your thighs slope slightly downward. Your weight should be evenly distributed in a tripod pattern, represented by your seat pan and each foot on the floor. Find your neutral pelvic position by alternately arching, then slouching the low back. Find a comfortable position between the two, and stabilize by pulling navel to spine. Hold this position. Bring the backrest forward to snugly contact the curve of your lowback. Have someone else adjust your armrest height so your arms feel fully supported and relaxed, without visibly elevating the shoulders. (Note: If at the highest adjustment your thighs are parallel with the floor, or only very slightly sloping downward, consider ordering a taller cylinder. On the other hand, if you cannot sit all the way back on the seat pan with your weight equally distributed through each foot and buttocks at the lowest adjustment, try a shorter cylinder.)

Air-Filled Seating

a

b

c

Studies show that a stool that allows frequent spinal movement may be beneficial in reducing low-back pain.13 These stools may incorporate an air-filled bladder component into the design that follows the operator’s pelvic movements (Figure 5a). This design may also balance the muscle activity in your core stabilizing muscles between the abdominal and lumbar areas, thus improving your working posture. These designs encourage active sitting while not constraining the pelvis to one position, as found in sitting on a traditional, flat seat pan. These innovations allow movement of the spine and pelvis by adapting to your body as you move, not vice versa. Nontilting seat pans may be retrofitted with a wedge-shaped, air-filled cushion to achieve better ergonomic seating and to fully gain the benefits of an air-filled seating system (Figure 5b).
Exercise balls are common fitness tools used by therapists in building patients’ postural core strength. These ball chairs work well in larger operatories, front office areas, and orthodontic or pedodontic operatories. Most ball-seating systems offer leg extensions to accommodate taller workers (Figure 5c).
Another way to simulate spinal movement is to alternate between 2 different seat styles. Consider using a traditional stool (with or without armrests) in one operatory and a saddle-style or air-filled bladder stool in another. Each design uses very different groups of muscles. Also remember to consider intermittently standing for some procedures.

CONCLUSION

The proper selection and adjustment of operator stools play a key role in the management and prevention of work-related pain in dentistry. Since dental equipment technology is constantly changing and advancing, dentists should visit tradeshows to gain knowledge of the most recent offerings in these areas.

References

Ms. Valachi is a physical therapist, dental ergonomic consultant, and author of Practice Dentistry Pain-Free: Evidence-based Strategies to Prevent Pain and Extend Your Career. She is president of Posturedontics, a company that provides research-based dental ergonomic education, and is clinical instructor of ergonomics at OHSU School of Dentistry in Portland, Oregon. She lectures internationally to dental organizations and has produced exercise videos specifically for dental professionals. She offers free articles and operator stool reviews on her Web site at posturedontics.com, and can be reached at (503) 291-5121 or bethany@posturedontics.com.

Figure 1. Early sitting techniques did not usher in a significant improvement in operator ergonomics.

Unfortunately, most in the field treated these great technological successes as the end of the journey, as we turned our attention to the other great opportunities our blossoming profession has created. Scientific effort was transferred to ancillary devices (such as curing lights, resins, intraoral cameras, etc) that served to broaden the scope of services, further stimulating the profession’s ascendance. Today, a general dental practitioner’s income is greater than that of a family physician’s.

However, this success is not without its problems. Low back pain is the leading cause of occupational disability in dentistry. Studies clearly show that low back pain is frequently related to sitting duration. When sitting was first introduced to dentistry, most dentists spent their day doing amalgams. The procedures were fast and easy. Today, with the wide range of services offered, many practitioners find themselves in a fixed seated position for extended time periods—a situation that is extremely deleterious to the spine and to physical health in general.

The evolution to the seated position is just the beginning of our journey. A new look at dental practitioner positioning must occur as we pursue greater performance, and as a result, incomes comparable to other surgical professionals, behind which we currently lag. In order to discover how to minimize problems protracted sitting causes and gain the maximum benefit from the advantages sitting offers, it would be helpful to know a bit more about the spinal column—how it works and how spinal health relates to sitting.

Many experts in the field believe sitting is, in fact, not a particularly healthy position,  but that it just happens to be the most practical position from which to operate machines. Some, such as Dr. Galen Cranz of the University of California, have argued that in preindustrialized society the seated position existed solely for ceremonial purposes. Many civilizations, such as Japan and India, did not utilize chairs throughout thousand of years of their development.

The human spine and its support musculature is a living structure that benefits from movement. Our shock-absorbent disks must have motion in order to be nourished properly. Any attempt at physically constraining the spine in a so-called “proper position” will ultimately meet with failure. If there can be no perfect position, by definition there can be no perfect chair. The best chair will be the seat that in the context of the task to be performed minimizes the damage done by sitting while allowing its occupant to transition through the hundreds of postures, all of which vary in their level of imperfection.

So, if the seat is our best hope for a productive dental practice and yet it still has the potential for damaging our health, how should we study and improve sitting? What are the criteria for a great operator stool?

Figures 2a and 2b. Improper positioning and poor stool selection encourages stressful practice habits.	2b.

Beginning with training in most dental schools, the young practitioner learns to accommodate to institutional equipment often purchased primarily for its price and durability or as part of a complete equipment package. Support, the reason for a chair’s existence, is relegated to a position of minor importance, or worse, ignored (Figures 2a and 2b). After graduation, when faced with the expense of an office start-up, many items supersede the young practitioner’s attention to seating. Worries about the cost of x-ray machines and handpieces, as well as attracting patients, easily overshadow concerns about a place to sit. And so the limber young professional begins a career filled with awkward positions day in and day out. It seems that ergonomics, and with it proper seating, only emerge as priorities once discomfort or injury encroach, thus adding the need for a chair to rehabilitate as well as support the practitioner.

While it is to a certain extent true that there are a wide range of apparent seating preferences, these preferences break down into a limited number of discrete characteristics. If you know where you want to go, it is without question easier to determine how to get there. Just as a bed is your most used and thus most important piece of household furniture, so should the operator stool be at the center of your office ergonomic purchasing plan, because its contact and use shapes the overwhelming percent of your day.

Let’s begin to look at the ideal operator’s stool from the ground up in order to ensure the support that is right for you and your practice. Follow-ing are 8 keys to selecting the proper stool.

NO. 1: CAST STAR BASE CONSTRUCTION WITH HIGH-QUALITY CASTERS AND BEARINGS

There is no clerical office task that requires as much micromotion as does clinical dental practice. The dental stool moves almost every minute as the operator adjusts to improve visual access and as he or she  accommodates patient movement. Casters must be able to respond rapidly to these requirements. In addition, the support base itself must bear the repeated stress of an operator’s continuous chair entry and exit over years of function. A dental stool should, therefore, be constructed using a rigid cast framework that will not distort with time and use. A 1-piece casting is less likely to distort and thereby rock with time. This rigid base must accommodate 5 casters to prevent rearward tipping; however, the base should not be as wide as that of many office chairs. Dental stools must have a compact base so that the wheels do not interfere with the feet, the foot controls, or the patient chair.

NO. 2: FULLY ADJUSTABLE HYDRAULIC GAS LIFT

Figures 3a and 3b. A wide variety of postures are ergonomically acceptable and provide for great practitioner flexibility.	3b.

During the workday, dentists are confronted with a wide assortment of patient sizes and restrictions. These variations should not cause the level of operator stress and strain that dentists seem to believe they must. In order to accommodate this wide range of sizes, shapes, and positions, a dental operator stool must have a hydraulic piston assembly that allows the widest range of motion. It is recommended that a shorter operator have a stool adjustment range from 16 to 21 inches and a taller individual have a range of 21 to 26 inches. Dental assistants need to be able to function from 20 to 31 inches, depending on doctor height. In most North Amer-ican dental offices, the assistant will sit at least 4 inches higher than the doctor in order to ensure a clear sight line to the oral cavity. While virtually none of the operator seats on the market cover a range of 16 to 26 inches, a limited number of specialty dental stools will accommodate most of this range of motion. In an ideal situation an operator should be able to function from a height range where thighs are parallel to the floor through a full legsupported position referred to as “sit-standing” (Figures 3a and 3b). Sit-standing is especially useful for posture-compromised patients who are unable to lie back in a full re-cumbent position, and on occasion, when dealing with highly apprehensive individuals.

NO. 3: TRUE WATERFALL-STYLE SEAT SUPPORT

Figure 4. Waterfall seat front.

Today it seems that every product that touches our lives is being described as ergonomic. All too often, this ergonomic claim is due to some minor modification, or worse, simple relabeling of a product. In seating, we see the softening of a chair’s leading edge being cause to suddenly create a so-called ergonomic seat. A soft seat front does not make an ergonomic chair. True ergo-nomics must generally be built into a product, not just tacked on (Figure 4).

Figure 5. Leg-balanced sitting provides traditional support.

True waterfall design, while just one of a number of concepts in ergonomic seating, is an essential principle. Your chair must be designed so that the seating position can be slightly elevated beyond the parallel without restricting blood flow to the legs. This allows an operator to maintain a forward and upward posture while operating and transfers some of the body’s support to the feet. We refer to this as “leg balanced sitting” (Figure 5).

NO. 4: RAPID AND EASY-TO-USE ADJUSTMENTS

Figure 6a. Complex adjustments should be reserved for those  situations where it is unavoidable.	Figure 6b. Single-lever, 3-way adjustability with separate back height adjustment.

All too often, we are led to believe that more complexity results in an improved product. In reality, nothing could be farther from the truth. Studies in many industries have shown time and again that users need both adjustability and simplicity in the products they use. Your seating must be rapidly and easily adjustable by all users. Complex mechanisms will rarely be used in the way they are designed to be. The simplest fully adjustable mechanisms have a single lever that activates both height and base tilt while allowing back height to be adjusted directly at the backrest (Figures 6a and 6b).

NO. 5: STRONG FORWARD BASE-TILT CAPABILITY

Figure 7. Strong forward tilt of the seat is a unique requirement for dental operator stools.

Dental health workers do not operate from a position that is in any way equivalent or similar to that of typical clerical office workers. Dentists are universally subjected to a forward (and hopefully upward) proclination. The seat support mechanism required must reflect this special circumstance. It must be forward adjustable to remind the operator’s lower back to maintain its natural curve. This reminder is more important than the seat back actually supporting the operator. If you think about this for a minute, you can’t really support someone from behind if they are leaning forward! Most so-called dental stools do not allow this posture and instead are vinyl-covered variants of basic office seating. Correct dental seating should allow an individual no less than 20° of positive forward support. Adjustment should be quick and accommodate a wide range of postures (Figure 7).

NO. 6: STRONG LUMBAR SUPPORT WITHOUT SHOULDER IMPINGEMENT

Figure 8. Deep lumbar support with freedom at the shoulder.

Dentists are not sitting in treatment rooms to read books or take naps, yet all too often purchasing decisions are made based on a seat’s apparent comfort at a trade show or dental showroom—away from patient treatment. As a result, operators often will select a seat better suited for the private office than the operatory. The lumbar mechanism should allow an adjustment range that positions the lumbar support well into the operator’s low-back curvature (Figure 8). The backrest should not be so tall as to prohibit the natural curvature of the spine. Many contemporary operator stools are equipped with a backrest that is far too tall and wide to allow operator motion flexibility. This can interfere with shoulder mobility. Excessive width is an additional problem that prohibits close work from the 7 o’clock position.

NO. 7: FIRM, SUPPORTIVE SEATING SURFACES

Figure 9. A firm, contoured seat permits support during lateral motions.

As dental providers, we sit on a stool for balance and support. Thick padding that may feel elegant during a demonstration prohibits maximal extension laterally during dental use. Unlike office workers, we must frequently function off-axis. Only a contoured seat firmly padded with the highest quality foam core is able to permit this motion safely (Figure 9). A softer padded seat that has contour built into the pad rather than the base gives way during lateral reach motions and re-quires the operator to strain during extension.

NO. 8: OPTIONS FOR PERSONALIZATION

While arm support is a controversial subject, many operators and experts feel they are essential to health and comfort. Some physiologists believe that lack of adequate arm support is a primary contributor to thoracic outlet syndrome and carpal tunnel, though this has not been clearly demonstrated. The capability to add highly supportive arms that function through a wide range of motion is an option that any modern dental stool should provide.

Figure 10. Unique, fully articulating elbow rests.

When a dental stool is outfitted with arm support, the arms may be fixed in length but must allow rapid height adjustment and full articulation. If you find yourself leaning on nearby cabinets or resting your arm on your patient’s head, then you  need a new stool, a new position to practice from, and possibly support arms (Figure 10).

CONCLUSION

The dental operator stool is a most vital and often neglected piece of dental technology. It is a lifeline to long-term practitioner health and productivity. Perhaps no dental acquisition is more personal than this purchase. Choose wisely for a prosperous and healthy future.

Dr. Ahearn is the founder of Design/Ergonomics (design-ergonomics.com), a design and consulting group that creates high-performance dental office designs and consults with doctors and universities regarding productivity constraints. He can be reached at (508) 636-3600 or djahearn@desergo.com.

As a result of working conditions, the dentist’s anterior neck, hip, and chest muscles become tight and shortened. Thus, the dentist becomes frozen in a flexed position with the shoulders, neck, and back functioning in a less-than-ideal position.

As an analogy, imagine the chest and anterior neck muscles as coiled springs, which are pulling the head and shoulders forward. The back muscles can pull the shoulders and head back through voluntary contraction. But, as soon as the back muscles are released, the head and shoulders move forward again.

 The pelvis, which is the foundation for the spine, is also often rotated or tipped. This forces the spine to compensate with a series of curves from the low back up to the neck to keep the head erect. Thus, you will notice that many of the exercises in the short program discussed in this article are related to releasing tight leg and hip muscles. For example, shortened and tight hip flexors (illiopsoas) and quadriceps (rectus femoris) can cause the pelvis to tilt forward, causing increased curvature of the low back as well as a protruding abdomen. In addition, these tight muscles prevent the gluteus maximus/medius and lower abdomen from functioning properly.

 Performing self-myofascial release (SMR) using both the foam roll and medicine ball will help release these muscles, allowing them to return to their normal length. This activity will help decrease low back pain and allows the lower abdominals and gluteus maximus/medius, key muscles in core stability, to begin to function normally.

The emphasis in this program will be placed on releasing shortened, tight muscles in the chest, anterior neck, and hips. While the dentist generally perceives pain only in areas of the back, this pain will not be relieved until the shortened, tight anterior muscles in the neck, chest, and hips are released. This allows the elongated, weakened muscles of the back to return to their normal length and function.

This program is unique in 3 ways:

(1) it requires a minimum amount of equipment;

(2) it can be done in one’s home or office; and

(3) a minimum of time is required, and the program actually works best if it is broken into segments through-out the day.

The dentist-author had endured varying degrees of back and neck pain with only moderate levels of relief from various modalities until a program developed specifically for dentists was instituted. Co-authors of this article, Domenic Pompile, a physical therapist and certified strength and conditioning specialist, and Rick DeLopez, a certified strength and conditioning specialist, developed this unique program. By using this program, the author experienced immediate improvement and significant relief from chronic back and neck pain. This resulted in physical stress relief while working, higher energy in general, a decrease in nonsteroidal anti-inflammatory utilization, and deeper and more restful sleep. (Sounds too good to be true, doesn’t it?)

SELF-MYOFASCIAL RELEASE TECHNIQUE FOR THE DENTIST/TECHNICIAN (A PHYSICAL THERAPIST’S PERSPECTIVE)

  Myofascial release is commonly used by many practitioners to loosen soft tissue and allow increased ranges of motion and flexibility in order ultimately to decrease pain and improve function. Unfortunately, many times the results may be temporary due to a number of reasons. But the fact still remains that the individual continues to suffer from discomfort,  lack of range of motion (ROM), and lack of strength.

Many individuals attempt to alleviate their symptoms by increasing the strength or loosening the muscles or areas that they feel are troublesome. One common problem is that many patients try to loosen or strengthen their area of discomfort, but commonly receive little or no relief at all from their original symptoms. The reason for this is that the individual is incorrectly trying to release or loosen the muscle that is impeding his or her function. In other words, the individual has not been able to identify the true root of the problem and in essence is just putting a Band-Aid on the situation.

For individuals who are fixed in a static position for a lengthy period of time throughout the day, many postural changes take place. In turn, this will lead to a shortening of certain muscles in the body as well as a lengthening of the opposing muscles. For example, a dentist may be seated in a chair with the hips at 90º of hip flexion, the trunk rotated and side bent, along with an increased forward head posture. Many dentists may be fixed in this position for lengthy periods of time throughout the day, and this will lead to a shortening of many of the anterior structures as well as a lengthening of many posterior structures. Ultimately, as the anterior structures continue to become shorter and tighter, the posterior structures become lengthened, weak, and painful. Normally, due to the large degree of neck, shoulder, and back pain, the clinician may receive treatments to alleviate the discomfort, emphasizing the site of their pain along with soreness and tenderness. Unfortunately, due to the static positioning that continues to take place, the clinician will continue to become more and more tight anteriorly. However, he or she will continue to experience the majority of the symptoms posteriorly in the back of the neck and low back or experience a lack of ROM in the shoulders. The clinician may be aware of this static positioning, but unfortunately, this positioning is a part of the job with little or no ability to change. With this in mind, we must then clearly define the root of the problem and also assess and effectively treat the anomalies that it presents.

By instituting a 20-minute stretching and self-myofascial release program, the clinician will be able to lengthen the structures significantly that have become so tight due to this static positioning. He or she will also be able to shorten the lengthened muscle fibers in order for them to fire again and work more efficiently in maintaining proper posture. Ultimately, this will lead to a decrease in pain, increased joint range of motion and strength, and an increase in the present level of function.

Our program is designed to lengthen anterior structures systematically such as the pectoral, quadricep, illiopsoas, anterior cervical, and deltoid musculature. In turn, lengthening these tight anterior structures will help return the posterior muscles to their normal resting length, and they will begin to work more efficiently by giving support and maintaining posture.

These posterior structures will also become less painful, since they will not be working overtime to straighten the cervical or lumbar spine, as we have already released the spastic anterior structures. Our goal is to “open up” the individual by decreasing tightness and treating the root of the problem at hand. Strengthening the posterior structures is a very integral part along with stretching, but unless you begin to treat the root of the problem that is causing the dysfunction, the dysfunction will always remain. The program will also offer strengthening and stabilization activities to the low back, trunk, and neck along with numerous self-myofascial release techniques.

Briefly describing exercises in an article with a limited number of pictures is a challenging task. (For this reason, we have developed a DVD with stretches and a few exercises designed specifically for the dentist and technician). If you will work through the descriptions of the exercises using the pictures as references and do this simple workout, you will be amazed at how quickly you gain significant relief from chronic neck, back, and shoulder pain that is often associated with practicing dentistry.

HOW SELF-MYOFASCIAL RELEASE WORKS

When a muscle is placed between a foam roll or medicine ball and the patient’s weight, that muscle stretches. This stretches the tendon, which compresses the golgi tendon organ, and that muscle is signaled to elongate. At the same time, pressure is applied to a sore spot (latent trigger point) that causes hypoxia followed by a reactive hyperemia, and the pain at that spot decreases significantly in 25 or 30 seconds.² When this technique is repeated for a few weeks, the sore spots (TPs) often disappear, and the muscle returns to a more functional length.

Stretches to be Done in the Office Daily

It is strongly recommended that all individuals consult with a physician prior to beginning these activities.

Figure 1. The doorway stretch can be performed 2 or 3 times daily, between patients.	Figure 2. The thoracic/scapular stretch can be preformed once or twice daily. This exercise can be very relaxing, as is the stability ball stretch shown in Figure 3.

(1) Doorway Stretch: Per-form this exercise 2 or 3 times daily, between patients. Stand in a doorway and raise one arm out to the side approximately 90º. Place the forearm on the back of the door jamb with palm facing forward. Draw in the belly button and slowly bring the same side leg forward until a slight stretch is felt in the chest and anterior shoulder. Keep your shoulders even, making sure that the opposing shoulder does not roll forward. Hold for 25 to 30 seconds, then repeat with the other arm (Figure 1).

Stability Ball Exercises

Figure 3. The stability ball stretch. Draping your body over the ball, extend your arms out to the side and allow gravity to pull your arms toward the ground. Hold this position for 30 to 45 seconds.

(1) Stability Ball Stretch: Sit on a stability ball. Slowly walk your feet out and lay back on the ball, draping your body over the ball. Extend your arms out to the side and allow gravity to pull your arms toward the ground. Hold this position for 30 to 45 seconds (Figure 3).

Figures 4 and 5. Bridging on stability ball. Lie on the floor with arms straight out to your side and palms facing down for balance. Place the ball under the back of your knees. Draw in your abdomen and slowly lift your buttocks off the floor so only your arms and shoulders are touching the floor. There should be a straight line between your knees and shoulders. Squeeze your buttocks together, contract your abdomen, and hold for 2 to 3 seconds, then slowly lower to the floor. Repeat this exercise 10 to 15 times.

(2) Bridging on Stability Ball: Lie on the floor with arms straight out to your side and palms facing down for balance. Place the ball under the back of your knees. Draw in your abdomen and slowly lift your buttocks off the floor so only your arms and shoulders are touching the floor. There should be a straight line between your knees and shoulders. Squeeze your buttocks together, contract your abdomen, and hold for 2 to 3 seconds; then slowly lower to the floor. Repeat this exercise 10 to 15 times (Figures 4 and 5).

Figures 6 and 7. Bridging on the stability ball lowering hips. Bridging on the stability ball strengthens your lower back, abdomen, and hips.

(3) Bridging on the Stability Ball Lowering Hips:  Sit on the stability ball, slowly walk your feet out, and lay back on the ball. The head and shoulders should be resting on the ball with the neck in a neutral position. Slowly lower your hips, directing the tailbone toward the stability ball. Then lift hips up slowly toward the ceiling; the chest should be lifted up with the shoulders, hips, and knees aligned in the position of a plank. In this position, contract your abdomen and buttocks and hold for 2 to 3 seconds. Don’t allow your legs to move in or out, and keep the ball from moving. Perform this exercise 10 to 15 times. Bridging on the stability ball strengthens your lower back, abdomen, and hips (Figures 6 and 7).

Figure 8. Scapular retraction/protraction on stability ball can be performed in 2 sets of 10 to 12 repetitions.

(4) Scapular Retraction/ Protraction on Stability Ball:  Lying on your back draped over the stability ball, slowly reach your arms toward the ceiling with your palms facing in until your shoulder blades are raised off the ball. Next, keeping your arms straight, begin to retract your shoulders toward the ball and pinch your shoulder blades together; hold for 2 to 3 seconds. Perform 2 sets of 10 to 12 repetitions (Figure 8).

SELF-MYOFASCIAL RELEASE USING THE FOAM ROLL AND/OR MEDICINE BALL

These exercises can be done at any time of the day and can be done incrementally.  For example, they can even be done while watching television at home.

Pectoralis Major/Minor

Figure 9. Pectoralis major/minor. Place a small medicine ball on the wall and lean into the ball, placing it under your clavicle between the shoulder and sternum. Roll the ball up and down and side to side until a tender spot is located. Hold position on tender area until a release in the muscle is felt (approximately 30 to 45 seconds). Repeat this activity on the opposite side.	Figure 10. A more advanced version of the pectoralis major/minor exercise is performed while lying in a prone position.

Place a small medicine ball (approximately 2 pounds) on the wall and lean into the ball, placing it under your clavicle between the shoulder and sternum. Roll the ball up and down and side to side until a tender spot is located. Hold position on tender area until a release in the muscle is felt (approximately 30 to 45 seconds). Repeat this activity on the opposite side (Figure 9). A more advanced version of this exercise is performed while lying in a prone position as is pictured in Figure 10.

Quadriceps

Figure 11. Quadriceps. Begin by lying prone with a foam roller under your thighs. Slowly roll your legs up to the hips and then back down to the knees using either your feet or upper body for assistance. Hold roller on tender spots for 30 to 45 seconds.

Begin by lying prone with a foam roller on your thighs. Slowly roll your legs up to the hips and then back down to the knees using either your feet or upper body for assistance. Hold roller on tender spots for 30 to 45 seconds (Figure 11).

Illiotibial Band

Figures 12 and 13. Illiotibial band. This exercise will be very uncomfortable initially and should be performed slowly.

Lie on your side with a foam roller under the side of your thigh. Raise the bottom leg slightly off the floor. Roll from the hip to the knee on the lateral side of the thigh. Hold tender spots 30 to 45 seconds. This exercise will be very uncomfortable initially and should be performed slowly. Repeat on opposite side. The top leg can be bent and the foot placed on the floor in front of the lower leg to decrease the pressure placed on the illiotibial band for the first week or so if you find this exercise painful (Figures 12 and 13).

Tensor Fascia Latae

Begin by lying with a foam roller under your thighs (quadriceps). Next, place the foam roller just lateral to the anterior pelvic bone about halfway between the positioning for the quadriceps and illiotibial exercises. Slowly roll on the foam roller until a tender spot is located. Hold this position for approximately 30 to 45 seconds or until tenderness has decreased by approximately 75%. Repeat the activity on the opposite side.

Illiopsoas

Figure 14. Illiopsoas. Place a small medicine ball on the wall and lean into the ball, placing it on the anterior hip. Roll the ball in small circles until a tender spot is located.	Figure 15. The advanced version of the illiopsoas exercise is performed while lying in a prone position. This is an important SMR exercise.

Place a small medicine ball on the wall and lean into the ball, placing it on the anterior hip. Roll the ball in small circles until a tender spot is located. Hold this position for 30 to 45 seconds. Repeat on opposite side (Figure 14). The advanced version of this exercise is performed while lying in a prone position as is shown in Figure 15. This is a very important self-myofascial release exercise.

Latissimus Dorsi

Figure 16. Latissimus dorsi. Lie on your side with arm outstretched and thumb facing up. Place foam roller slightly below armpit and slowly move back and forth until a tender spot is located. Hold for 30 to 45 seconds. Repeat the activity on the opposite side.	Figure 17. Piriformis. Begin activity by sitting on a foam roll with arms placed just behind you for support. Next, cross the foot of one leg over the opposite knee and slowly roll on the posterior aspect of the hip of the crossed leg. Once a tender spot is located, hold for approximately 30 to 45 seconds. Repeat activity on the other side. Expect this muscle to be very tender initially.

Lie on your side with arm outstretched and thumb facing up. Place foam roller slightly below armpit and slowly move back and forth until a tender spot is located. Hold for 30 to 45 seconds. Repeat the activity on the opposite side (Figure 16).

Piriformis

Begin activity by sitting on a foam roll with arms placed just behind you for support. Next, cross the foot of one leg over the opposite knee and slowly roll on the posterior aspect of the hip of the crossed leg. Once a tender spot is located, hold for approximately 30 to 45 seconds. Repeat activity on the other side. Expect this muscle to be very tender initially (Figure 17).

CONCLUSION

This is a relatively easy exercise program that really works. It requires a minimum amount of time and equipment, but can have a significant impact on how one feels while treating patients and, more importantly, how one feels all day every day.

These carefully selected exercises allow the individual to open up and regain and maintain more normal posture and function. Combining self-myofascial release with a few exercises on the stability ball is the key to this program. Performing each exercise is as vital as doing the exercises on a regular basis. It is worth the effort!

References

1. Valachi B, Valachi K. Mechanisms leading to musculoskeletal disorders in dentistry. J Am Dent Assoc. 2003;134:1344-1350.

2. Travell JG, Simons DG, eds. Myofascial Pain and Dysfunction: The Trigger Point Manual. Baltimore, Md: Williams & Wilkins; 1983:27.

Dr. Thomas DeLopez spent 3 years in the US Army as a dental officer and then entered private practice in Tallahassee, Fla, in 1974. He is the former president of the Leon County Dental Association and maintains a full-time practice that emphasizes restorative and cosmetic dentistry. Dr. DeLopez writes and lectures on crown and bridge dentistry and doctor/laboratory communications. He can be reached at drtomd@nettally.com.

Mr. Rick DeLopez, a former CPA and auditor, is a full-time strength and conditioning specialist in Boca Raton, Fla. He is a graduate of Florida State University and specializes in functional training to improve balance and core strength. In addition, he works at the Boca Raton Resort and Club as an exercise specialist, developing strength and conditioning programs for golfers and tennis players. He can be reached at (561) 702-9110 or rdelopez@hotmail.com. To order our DVDs, foam rollers, stability balls, and other fitness products, visit domric.com.

Mr. Pompile is a licensed physical therapist practicing in Boca Raton, Fla. He graduated from the University of Hartford with a bachelor of science degree and is also a certified strength and conditioning specialist from the National Strength and Conditioning Association (NSCA). He is involved in developing rehabilitative equipment for needs specific to postural dysfunction syndromes and has developed a shoulder machine specific for upper extremity postural dysfunctions, which will be available this year. He can be reached at (561) 417-2995 or dpomp76@aol.com.

In an effort to improve working comfort and reduce musculoskeletal disorders among dental operators, manufacturers have promoted multiple design concepts to the marketplace. Although it must be understood that the prevention of work-related pain and musculoskeletal disorders (MSDs) is a multifactorial issue,6 the choice of proper seating is critical and can either improve or worsen a clinician’s comfort and level of musculoskeletal health. It is the opinion of the authors that no ideal chair design exists for dental operators. We have also observed multiple instances of operators (dentists, hygienists, and assistants) using otherwise well-designed ergonomic chairs and stools improperly. This is often due to lack of knowledge as to how to adjust ergonomically designed chairs correctly, combined with a lack of understanding as to how these adjustments impact the biomechanics of the operators and their musculoskeletal health.

An important aspect of choosing and optimally adjusting chairs or stools for any individual operator is to understand the effects that a person’s height has on that choice. While it is obvious that people purchase shoes or clothing that fit properly, it seems to be far less so for dental professionals when choosing the chairs that they spend a significant portion of their careers upon. Although many manufacturers provide options to accommodate different operators’ heights and body sizes, many are sold with standard features that have been designed based on a statistically average-sized person (usually a man). These features may fit and support some operators well, but can cause multiple problems for others.

CHAIRS VERSUS STOOLS

Some confusion exists in the dental profession as to what differentiates a dental stool from a chair. Technically, a stool does not have a back or armrests, so the majority of seating available to dentists today are chairs. Perhaps in an effort to avoid confusion, dental manufacturers frequently refer to patient seating as chairs and doctor seating as stools. For the purposes of this article, we will distinguish between the two, considering both chair and stool designs for the dental operator.

SEAT TILT AND LOW-BACK PAIN

Figure 1. Sitting with thighs parallel to the floor promotes flattening of the lumbar spine.

Most dentists and hygienists were taught in school to sit with thighs parallel to the floor, or hips at a 90º angle. This paradigm for seated work has been widely accepted for generations and may be due in part to the design of early operator chairs, which featured flat, nonadjustable seat designs. The nature of dentistry makes intermittent forward leaning virtually unavoidable. This combination of thighs parallel to the floor with forward leaning causes the pelvis to roll backward, promoting flattening of the low back curve^7,8 (Figure 1). Research shows that this flattening of the lumbar curve has detrimental effects upon both the spinal musculature and discs. Muscular activity in the lower back increases, which can cause ischemia and painful trigger points. Pressure within the disc also increases, which can lead to premature disc degeneration. The research therefore supports the concept of positioning hips higher than knees, allowing for an increased hip angle with lower associated low-back muscle activity and disc pressure.^7,10

Figure 2. A tilting seat helps maintain the low back curve, reducing muscle and disc pressures.

Chairs with a tilting-seat feature as well as saddle-style stools enable the hip angle to open to greater than 100º, which helps maintain the low back curve, decreases disc pressure, enables closer positioning to the patient, and may help reduce low back pain^7,10 (Figure 2). It is essential for operators to maintain—as best as possible—the normal curvature of the spine while working.

TALL AND SHORT OPERATORS

In general, tall operators with long trunks tend to have a higher incidence of low-back pain. This is partly due to gravitational forces acting on a longer lever arm when the operator assumes any degree of forward leaning. On the other hand, many dentists with shorter torsos tend to have neck and shoulder pain due to arm elevation when the patient is placed at lap level.

In the past, operator chairs were often designed for the average man. This trend is changing in response to the evolving demographics of the dental profession in which approximately 70% of operators (dentists and hygienists combined) are now women.¹¹ It is common, however, for stools and chairs to be sold “as is,” offering standard features and little regard to the special needs of individual operators. Fitting a standard seat with a short or tall cylinder may allow operators to maximize the ergonomic benefits of the chair. Therefore, special considerations are need-ed for tall and short operators.

Considerations for Taller Operators (Generally 5’10” and Over)

Figure 3. Pivoting forward properly from the hips allows the operator to maintain the 3 primary spinal curves.

Tall dentists with long torsos are most prone to flattening the low back and should pay particular attention to strength-ening of the transverse abdominal muscles. These muscles can be used throughout the day to regularly stabilize the low back curve,^12,13 especially with forward leaning. The following “operator pivot” exercise recruits these muscles to stabilize the spine (Figure 3). While this exercise is especially helpful for tall dentists with long torsos, all operators can benefit by incorporating it into their daily routine:

•Sit tall on the stool with a slight curve in the low back.

•Assume an operating position with the arms.

•Exhale, and actively (with your muscles) pull your navel toward your spine. Your transverse abdominal muscles are now helping maintain your low back curve. (One common mistake is to suck in one’s breath to pull the spine toward the navel. You should still be able to talk, breathe, and move while holding this contraction.)

•Using the hips as a fulcrum, pivot forward from the hips, maintaining the abdominal contraction throughout the exercise.

•Strive to make this exercise a habit throughout the workday anytime you must leave a balanced sitting posture.

•A tilted seat pan or saddle-stool design will facilitate pivoting from the hips, making this exercise easier.

Figure 4. Proper adjustment of an ergonomic chair. (Chair courtesy of Orascoptic Research.)	Figure 5. A tall cylinder helps taller operators position themselves correctly.

Assess the height of the chair (Table) to evaluate whether a tall cylinder is required (Figure 4). If, at the highest height adjustment, your thighs are still parallel to the floor or your lower legs must be tucked underneath the chair, consider requesting a taller cylinder from the manufacturer (Figure 5). Often, this is simply the cylinder from the same model assisting stool.

Longer-legged operators should also assess seat pan depths of various chair and stool designs, as operator seat pan depths may range from 14 to 17 inches deep. The thighs should be well supported with feet flat on the floor. Taller operators should always raise the patient chair to a height that promotes their own best posture while conversing with the patient or consulting chair-side. This will allow for a more neutral posture during these times. A few minutes here and there add up over the course of a 20- to 30-year career in dentistry and can exacerbate existing musculoskeletal problems.

Magnifying scopes are an important ergonomic consideration for all dentists, but especially so for taller operators. It is nearly impossible for a tall dentist with a long torso to delivery quality dentistry with the patient at lap level and still sit upright. Make sure the working distance is measured in your own operatory (eye to working surface) with arms relaxed at your sides.

Considerations for Shorter Operators (Generally 5’ 4” and Under)

It is common to see shorter dentists with legs positioned under the patient, perched on the edge of the chair, arms abducted away from the body, and neck twisted to gain better visibility. This is commonly due to a positioning challenge related to the operator’s smaller stature. Even with the patient positioned correctly at lap level, simply the thickness of the headrest combined with the height of a patient’s head may cause some operators to elevate the arms—a contributing factor to neck pain. The challenge is to position the patient low enough to operate with arms in a relaxed, neutral posture. Opening the hip angle, utilizing a shallower seat pan, and use of a shorter cylinder are considerations for these dentists.

Figure 6. A saddle-style stool opens the hip angle, allowing lower positioning of the patient. (Bambach saddle stool courtesy of Hager Worldwide.)

The greatest hip angle may be obtained with the use of a saddle-style stool (Figure 6). This places the pelvis in a position that facilitates maintenance of the low back curve. By opening the hip angle up to approximately 140º, the stool allows for lower positioning of the patient and also closer positioning of the operator to the patient. The seat pan of a chair should be shallow (14 to 15 inches) and not touch the backs of the knees when seated all the way back in the chair. Assess the height of the chair (Table) to see if a shorter cylinder is required. You may need to request a shorter cylinder if, at the lowest adjustment, the following situation occurs:

•You cannot sit all the way back on the seat without easily fitting 2 to 3 fingers between the edge of the seat and the back of your knee.

•You do not feel weight evenly distributed through both legs and your buttocks.

•You feel you have to perch on the edge of the chair.

Other Considerations

Armrests are helpful in reducing neck and low-back strain for operators of all heights.14,15 Operators may consider the options of working with different styles of chairs and stools in different operatories as well as intermittently standing to spread the workload between different groups of muscles throughout the day.

CONCLUSION

Dental operators must become more educated regarding the impact of their choices in seat-ing in the operatory. Over a 30-year career, dentists and hygienists may spend upwards of 60,000 hours chairside or more than 1,800 days. Proper selection of chair/stool styles depends on many factors, and operators should try a stool or chair before purchasing it to assess how it fits their specific needs. However, even a well-designed chair or stool can detrimentally impact one’s musculoskeletal health if it is improperly equipped or adjusted for an individual’s body stature. The preceding guidelines should aid operators in their selection and adjustment of appropriate seating for the dental clinic.

References

1. Shugars D, Miller D, Williams D, et al. Musculoskeletal pain among general dentists. Gen Dent. 1987;35:272-276.

2. Rundcrantz BL, Johnsson B, Moritz U. Cervical pain and discomfort among dentists. Epidemiological, clinical and therapeutic aspects. Part 1. A survey of pain and discomfort. Swed Dent J. 1990;14:71-80.

3. Augustson TE, Morken T. Musculoskeletal problems among dental health personnel. A survey of the public dental health services in Hordaland. Tidsskr Nor Laegeforen. 1996;116:2776-2780.

4. Finsen L, Christensen H, Bakke M. Musculoskeletal disorders among dentists and variation in dental work. Appl Ergon. 1998;29:119-125.

5. Chowanadisai S, Kukiattrakoon B, Yapong B, et al. Occupational health problems of dentists in southern Thailand. Int Dent J. 2000;50:36-40.

6. Valachi B, Valachi K. Mechanisms leading to musculoskeletal disorders in dentistry. J Am Dent Assoc. 2003;134;1344-1350.

7. Harrison DD, Harrison SO, Croft AC, et al. Sitting biomechanics part 1: review of the literature. J Manipulative Physiol Ther. 1999;22:9:594-609.

8. Mandal AC. The Seated Man: Homo Sedens. 3rd ed. Klampenborg, Denmark: Dafnia Publications; 1985:28-29.

9. Karwowski W, Marras WS. The Occupational Ergonomics Handbook. Boca Raton, Fla: CRC Press; 1999:69-170,175,285,585-600,1134.

10. Hedman TP, Fernie GR. Mechanical response of the lumbar spine to seated postural loads. Spine. 1997;22:734-743.

11. White SW. Ergonomics…How does dentistry fit you? Women’s Dent J. 2003;1:58-62.

12. Hodges PW, Richardson CA. Inefficient muscular stabilization of the lumbar spine associated with low back pain. A motor control evaluation of transversus abdominis. Spine. 1996;21:2640-2650.

13. Hides JA, Richardson CA, Jull GA. Multifidus muscle recovery is not automatic after resolution of acute, first-episode low back pain. Spine. 1996;21:2763-2769.

14. Parsell DE, Weber MD, Anderson BC, et al. Evaluation of ergonomic dental stools through clinical simulation. Gen Dent. 2000;48:440-444.

15. Sahrmann S. Diagnosis and Treatment of Movement Impairment Syndromes. Philadelphia, Pa: Mosby; 2001.

Mrs. Valachi is a physical therapist, certified ergonomic assessment specialist, and owner of Posturedontics. A member of the National Speaker’s Association, she presents dental ergonomic seminars internationally and provides in-office ergonomic consultations to help dental professionals avoid injuries and extend careers. She is a published author in numerous dental journals, including the Journal of the American Dental Association, contributing author to a dental hygiene textbook, and author of the ADAA’s Ergonomics in Dental Assisting Home Study Course. She has also developed home exercise and chairside stretching video programs for dental professionals. She can be reached at (503) 291-5121 or stretchit@posturedontics.com. Upcoming seminars, ergonomic articles, and products are available at posturedontics.com.

Dr. Valachi operates a private family dental clinic in St. Helens, Ore. He co-founded Posturedontics and is a published author in dental journals, including the Journal of the American Dental Association. He has worked with dental manufacturers to trial, evaluate, and give recommendations for their ergonomic products and has provided insight to the development of an effective injury-prevention program for dental clinicians. He can be reached at (503) 291-5121, stretchit@posturedontics.com, or by visiting posturedontics.com.

In this article, we continue to look at the ways that dentists and hygienists perform their profession, starting with the work practices that predispose them to overuse the muscles, tendons, and nerves of their upper extremities. The risk factors involved with working with thin, sharp instruments away from the body are examined, and suggestions to reduce the amount of physical stress from instrument use are offered. The practitioner must also take personal responsibility for his own health by performing exercises and stretches both at work and at home, practicing stress management techniques, avoiding excessive use of his hands at home, and taking the necessary precautions to prevent the development of MSDs. Dentists can perform beneficial exercises/stretches every day (Figures 1 through 10) that will hopefully be incorporated into healthy lifestyle changes that support their ability to practice.

WORK PRACTICES

Dentists and hygienists are required to perform physically demanding work with the muscles of their arms and hands almost continuously throughout the day, while trying to provide the highest quality of care for each patient. They are often overbooked with heavy calculus patients scheduled back-to-back, requiring them to use excessive force with their hands without rest breaks in between. The procedures of probing, scaling, root planing, cleaning, polishing, and flossing the teeth are hand intensive and repetitive in nature, and when these are done in an improperly set up workstation for that individual practitioner the chances of developing repetitive injuries are multiplied. Dentists must look at the way they work, learn to pace themselves, and rotate between a variety of tasks and positions to give their muscles a break and allow them to work a full day without causing cumulative damage to their bodies. Changes in work practices are the easiest and least expensive alterations that can be made by the practitioner to reduce the stress of dental work.

Some of the risk factors that are involved in dental work practices include:

•Inadequate time per patient

•Overscheduling of patients

•Repetitive tasks performed without breaks

•Scheduling heavy calculus patients back-to-back

•Polishing each patient’s teeth

•Unchanging operator position

•Unchanging delivery system

•High pressure for quality care.

IMPROVING YOUR WORK PRACTICES

The following tips for improving your work practices can be incorporated into your daily routine to minimize or alleviate stresses placed on the body.

Schedule Enough Time for Each Patient

Using the hygiene patient as an example, the recommended amount of time that should be spent with each patient is 50 to 60 minutes for an adult and 35 minutes for a child. This is the ideal that should be strived for to allow the practitioner to have enough time to perform the procedures, write her notes, and prepare for the next patient. If there is time left over, the practitioner should perform exercises and stretches to increase circulation, decrease muscle tension, and prepare the body for the next patient.

Alternate Scheduling of Light/Heavy Calculus Patients; Use Selective Polishing

For hygiene patients, make a notation of the amount of calculus that a patient has when you see them, and ask the office staff at the front desk to schedule given patients at scheduled times of the day. Make sure that no more than half of your patients on a certain day are heavy calculus patients to spread the stress on your hands over many days.

Use selective polishing. If the patient is holding his part of the bargain and brushing and flossing each day, you may not need to polish his teeth, or you can spend less time on this task and put less stress on your hands. You could even offer a slightly discounted rate to these patients to reward their good oral hygiene.

Rotate Between Tasks

Give yourself time throughout the day to work on administrative tasks, patient charting, and other activities so your hands will have a break from direct patient care. By rotating tasks, you change the stresses that you are putting on your body, which gives various body tissues a chance to recover before being asked to perform the same motion again.

Schedule Rest Breaks Between Patients

To prevent repetitive injuries, it is better to pace yourself and schedule fewer patients per day, with rest breaks in between to allow yourself time to heal. During your break, you should perform nonstressful exercises, take walks, stretch, perform stress relaxation techniques, or just rest your hands.

Switch Between Positions Throughout the Day

Sedentary work, like that performed in dentistry, concentrates work stress onto certain muscles and builds tension in our bodies. By alternating between positions, you shift the stress onto different muscles, increase your circulation, and lessen the amount of fatigue from your work.

Vary Operator Position/Delivery System With Each Patient

If you always work on the same side of your patient with your delivery system in the same location, you will focus the stress of your work on the same muscles, which will eventually cause these areas to break down. By switching sides of the patient and altering the position of your delivery system, you will use your muscles in different ways, which will spread the stress over other parts of your body.

Gradually Increase Work Tolerance

If you have control over your work hours, try to gradually increase the amount of time that you spend doing certain tasks, so that your body has time to adjust to the new stresses that you are putting upon it. Communicate your needs to your colleagues, and try to work out a schedule that works best for everyone.

The instruments that dentists and hygienists use pose a special threat to the muscles and tendons of their arms and hands. They are required to forcefully grip thin instruments and make constant, precise movements with the small muscles of their hands and forearms throughout various procedures. Some of the most hand-intensive procedures that must be performed by dental practitioners are (1) probing, which requires high forces to be exerted by the hands; (2) scaling, which involves short strokes and the application of strong pressure; and (3) root planing, which requires longer strokes and more extensive ranges of motion in the wrists. Instrument usage involves all of the primary risk factors: repetition of movements; forceful exertions needed to manipulate the thin instruments; awkward postures of the wrists and fingers; contact stress on the fingers from the instruments; and harmful vibration effects from using ultrasonic scalers and drills.

Figure 1. Hip Circles. With legs apart and hands on hips, make circles with hips in clockwise and then counterclockwise motion. Begin with 10 repetitions and increase to 25.	Figure 2. Shoulder Circles. Move shoulders toward ears and then back trying to touch shoulder blades together. Repeat 15 to 20 times and then reverse direction.
Figure 3. Arm Circles. With arms at sides, make circles with arms out in front, over head, to side, and back down again. Make larger circles until arms move through their entire range of motion. Perform 15 to 20 repetitions and then switch directions.	Figure 4. Neck Exercise. With shoulders relaxed and arms at sides, bend head to one side, trying to touch ear to shoulder. Bring head back to center and repeat on other side. Progress from five repetitions to about 15 to 20.
Figure 5. Side Stretch. With legs shoulder width apart, lift arm over head while slowly bending torso sideways. Breathe and hold position for 15 to 20 seconds. Repeat on other side.	Figure 6. Shoulder Stretch. Clasp hand behind back with elbows straight and lift arms back behind you. Hold position for 15 to 20 seconds.
Figure 7. Overhead Stretch. Clasp hands together with elbows straight and lift arms over head. Breathe while stretching arms backward for 15 to 20 seconds.	Figure 8. Wrist Stretch. Extend arm straight out with palm facing up. With other hand grasp thumb and fingers of extended arm and slowly pull fingers backwards until you can feel a stretch over front of forearm. Hold position for 20 to 30 seconds and repeat on opposite side.
Figure 9. Forearm stretch. Extend arm straight out with palm facing down. With other hand push down on the back of hand until you can feel a stretch over the back of forearm. Hold position for 20 to 30 seconds and repeat on opposite side.	Figure 10. Prayer Stretch. Place palms of hands together in prayer-like position, fingers pointing up. Press wrists downward until you feel a stretch over front of wrists and into forearms. Hold for 20 to 30 seconds.

INSTRUMENT USAGE

Many problems have been noted with dental instruments, including the small diameter of the handles (usually between 3/16” to 4/16” in diameter), which requires a tighter grip to hold the instrument. Many instruments were designed with function in mind, without consideration of ergonomic factors or the possible effect on the body, and are unbalanced and require increased muscular force to manipulate. When dental instruments are not regularly maintained and kept sharp, more pressure may need to be applied to remove plaque and clean teeth. Additional problems are created by tight gloves and wristwatches, which decrease circulation and make it more difficult to manipulate dental tools. Instruments provide the practitioner/patient interface, but their use involves a number of harmful positions that greatly increase the practitioner’s hand stressors and may result in the development of MSDs.

Some of these harmful positions include:

•Extreme wrist flexion/extension, ulnar deviation, forearm rotation

•Repetitive grasping with thumb and fingers

•Excessive finger movements

•Firm grasp/excessive force needed to hold instruments

•Thumb hyperextension

•Pressure from instrument edges on fingers

•Vibration damage from vibrating instruments

•Tight gloves that constrict wrist/fingers.

Improving Instrument Usage

Adjustments in how you use various instruments can go far in affecting stresses on the hands and body. The following tips can help.

Use of Proper Instrumentation Techniques

Select the proper instruments for the task, and make sure to use good technique with the least amount of force necessary to perform the procedure. It is especially important to remember technique and ergonomic positioning when you are tired at the end of the day.

Use Larger Diameter, Balanced Instruments

Purchase high-quality instruments with large diameter handles that are easy to grip and balanced for less forceful manipulations. The cost of good instruments pays for itself when you factor this amount out over the number of years the instrument will be used.

Instrument Handles Should Be Rubber Coated With Waffle Iron Serrations

Because you work in a cold, wet environment, instrument handles should be rubber coated to retain heat and serrated to increase friction/decrease the force needed to grip the instrument.

Keep Instruments Sharp

Well-maintained, sharp instruments do a better job of cleaning the teeth with less physical work required by the practitioner, so instruments should be checked and sharpened on a monthly basis.

Use Ultrasonic Scalers and Slim Lines

Consider using ultrasonic equipment that reduces the amount of work that your hands must do to perform dental procedures. Make sure to dampen the vibration in these instruments to reduce the force needed to grip them and to prevent potentially harmful vibration from being transferred to the hand.

Alternate Grasp: Tripod and Three Chuck Grasps

The standard grip that dentists use with their instruments, the same as gripping a pen to write, puts stress on the muscles of the thumb, pointer finger, and wrist. Instead, try placing the shaft of the instrument between your pointer and middle fingers and use your thumb as a guide, which will take the stress away from gripping the instrument and shift it to other muscles.

Vary Between Intraoral and Extraoral Fulcrums

As a variation on holding your arms above the patient throughout the procedure, lightly rest your fingers on the patient’s teeth, using them as a fulcrum to move the instrument (intraoral), or rest your elbow on the side of the patient’s chair to take some weight off your shoulders and use your elbow as a fulcrum from which to work (extraoral).

Wear Properly Fitting Gloves

Watch out for gloves that are too tight or a watch that cuts off your circulation at your wrist. Order gloves in different sizes, so that all of the dentists who work in your office will have gloves that allow them to work with the least amount of restriction in their hands.

TAKE CARE OF YOUR OVERALL HEALTH

As health professionals, we often focus our efforts on providing care for our patients, without taking proper care of ourselves. When combined with work that causes us to repeatedly strain our muscles, tendons, and other body tissues, this physical stress can promote the development of MSDs through muscle tension, restricted movement, and pinched nerves. That is why it is very important to begin to take care of yourself, if you have not started already, and follow a regular fitness regimen and health routine that can be incorporated into your work week.

IMPROVING YOUR OVERALL HEALTH

Make regular physical and mental exercise part of your daily routine.

Keep Yourself in Shape

The best thing that you can do is to devote part of your day to keeping yourself in shape to be able to handle the stresses, mental and physical, that you accrue through work, and still keep a healthy attitude toward yourself and the people that you serve. This involves exercise, flexibility, proper nutrition, and staying active.

Perform Exercises/Stretches at Work

Take regular breaks throughout the day and stretch your back, shoulders, neck, arms, and fingers (Figures 1 through 10).

Be Aware of Stress Levels

Be mindful of your stress levels, and practice breathing, meditation, and stress reduction techniques to release any tension and keep you focused on what is important. Consider going to your local bookstore and selecting a book on the subject that would fit your temperament and that you would be willing to incorporate into your daily routine.

Avoid Hand-intensive Hobbies/Chores at Home

When you’re not working, you should try to avoid hand-intensive hobbies and obsessing over chores at home, because these add to the stress you are already putting on your body during the week. Do something else instead.

Get Enough Rest and Relaxation Time

Make sure you spend enough time with your friends and family, as well as doing things that are not work-related in your spare time, to keep a balance between work and play. Try to avoid stressful activities and make sure to get enough sleep to recover from your weekly stressors.

Be Aware of Pain Signals From Your Body

With the knowledge gained from this two-part series on musculoskeletal disorders, you can be more aware of the pain signals that you are receiving from your body and take the necessary steps to prevent these discomforts from turning into repetitive injuries.

CONCLUSION

If you apply the principles and suggestions that have been recommended, you will be able to reduce the stresses that you put on your hands and arms and greatly lessen the chances that you will develop a MSD or repetitive strain injury. By making small changes in your work practices, instrument usage, posture, workstation setup, and health practices, you can greatly affect your ability to provide quality care over a long, healthy, and successful career in dentistry.

Mr. Graham is an occupational therapist, hand therapist, and ergonomist who specializes in reducing the incidence and severity of repetitive strain injuries in dental offices in the San Francisco Bay Area. His company, Employee Ergonomic Services, provides injury prevention seminars, workstation evaluations, and ergonomic training for dentists to improve posture and efficiency and reduce costly injuries that threaten the livelihood of the dental practitioner. To earn continuing education credits while attending an on-site seminar, please contact Mr. Graham at (415) 821-3264 or colin@employeeergonomics.com. The seminar involves a PowerPoint or overhead presentation, problem-solving sessions, ergonomic workstation evaluations, demonstrations, and recommendations specific to the dental practitioners and hygienists, and it can be offered nationwide.