Positioning for Success:Essential Ergonomic Guidelines for Dental Hygienists

Twenty-five heads bowed reverently over their colleagues, diligently scaling the upper arch. From the back, one would assume that the students were not wearing loupes, but from the side, a dif ferent reality became apparent. The students were working on the upper arch with the occlusal plane angled slightly forward of vertical, causing excessive leaning and straining forward—even to see into the mirror. When the occlusal plane was tipped backward about 15 degrees, the postural transformation was amazing.

This is one of the most common ergonomic mistakes I observe, not only in the schools, but also among hygienists who have been practicing for over 20 years—those who own 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 hygienist’s optimal working posture.

Not feeling any pain…yet? Is a tooth completely healthy unless your patient is experiencing pain? The progression to an 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 1/3 of dentists who retire early are forced to do so because of a musculoskeletal disorder.13

• In 2004 approximately $131 million was lost in income due to MSDs in the dental profession.14

And the causes of MSDs in dentistry are multi-factorial, ranging from non-ergonomic loupes to improper selection of delivery system, 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 in dentistry. In fact, it has been shown that dentists who take the time to carefully position their patient to promote a direct view have significantly

fewer headaches. 15 Patient positioning techniques will vary slightly depending upon the quadrant being

treated, the patient’s tolerance to reclining, and patient chair shape and width.

by Bethany Valachi, PT, MS, CEAS

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Operator PostureFirst, it is imperative that the hygienist is seated

properly and the stool is correctly adjusted. 16 From an ergonomic standpoint, the operator stool is the most important chair in the treatment room. Its adjustment can profoundly impact your posture and musculoskeletal health. Positioning in the operatory should always begin with adjusting your operator stool first, then the patient. Ideally, the stool should be used by only one operator to prevent repeated adjustments. Keep in mind that a stool is only ergonomic if it adjusts to fit your body size and shape. When shopping for stools, it is wise to utilize unbiased product reviews.

The sequence for adjusting a traditional operator stool is as follows:• Adjust the backrest height so the most convex portion (the lumbar support) nestles in your low-back curve. On most dental stools, there is no recognizable lumbar support. On these stools, adjust the backrest to a height where the shape fits most snugly against the curves of your back.• Move the backrest away from your back, which enables you to sit all the way back on the seat pan.•Check for appropriate size of the stool by placing 3 finger-widths behind your knee. • If the closest finger touches the seat, the seat pan is too deep, and you should select a stool with a shorter seat. • If your stool has a tilting mechanism, tilt the seat very slightly forward, only 5-15°. • Adjust the height with your feet flat on the floor until your thighs slope slightly downward. Your weight should be evenly distributed in a tripod pattern: through each foot on the floor and through your buttocks. If, at the highest adjustment, your thighs are still parallel to the floor, you may need to order a tall cylinder from the manufacturer. • If the stool has armrests, adjust them one at a time to a height where the shoulder is not visibly elevated when compared with the opposite shoulder, yet the arm is fully supported.

If there is no tilting seat feature on the stool, an ergonomic wedge cushion may be used to retrofit the stool and at tain proper posture.

Saddle stools are becoming increasing popular among dental hygienists, since they are very easy to move around the head of the patient, facilitate proper posture at the 9 o’clock position, and are ideal for confined operatory spaces. Because of its shape, it places the pelvis in a neutral position, so the spinal curves can more easily balance and also minimizes the need for backrest support. Saddle stools are especially beneficial for shorter operators. By opening the hip angle, they allow lower positioning of the patient, and a more relaxed arm and shoulder posture. Saddle stool height should be adjusted so the thighs slope downward at about a 45° angle.

Patient PositioningSince the hygienist moves frequently around

the head of the patient during treatment, they will ask the patient to rotate the head or tilt the chin during treatment to at tain a line of sight that is perpendicular to the tooth surface.

Ideally, the patient should be positioned supine for treating the upper arch and semi-supine for the lower arch. However, in the real world, time constraints and practicality usually prevent the hygienist from such luxuries.

Therefore, it is recommended that the chair back be positioned so it is elevated 10-15° from the floor (Use the preset control of the patient chair to set this angle) and the headrest or dental positioning cushions used to control the angle of the occlusal plane when treating the upper and lower arches. Ensure that the positioning aid is not too large, or it will be counter-productive, forcing the patient’s head forward. Many ‘dog-bone’ pillows I have seen in operatories cause such positioning.

Af ter reclining the chair, 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 Of tentimes, this is not done in deference to the

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patient’s 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, low back and knees.

Fig. 1A & Fig. 1BAn ergonomic dental cushion (Crescent Products) will increase patient tolerance to being reclined when treating the upper arch, and facilitate proper positioning (Fig. 1A). Angle the headrest slightly forward when treating the lower arch (Fig 1B). (Photo ©2010 from “Positioning for Success” DVD)

When treating the upper arch, adjust the headrest so the occlusal plane of the upper jaw is about 15-20° backward in relation to the vertical plane. You can check for proper positioning from the side, using an instrument handle to visualize the angle of the occlusal plane. (Fig. 1A) This angle is most easily at tained with double-articulating headrests by angling the headrest upward into the patient’s occiput. On flat headrests, use a contoured dental pillow with the large end under the patient’s neck, to angle the head back and chin higher. Then, adjust the height of the patient chair so forearms are parallel to the floor or sloping 10° upward.17 Whether using flat or double-articulating headrests, contoured memory foam cervical support cushions will make the patient much more tolerant to reclining.

Side SettingIn the 8-9 o’clock position, the hygienist can

treat the upper posterior and anterior surfaces facing toward the hygienist, remembering to ask the patient to rotate their head to preserve their own best working posture. For instance, ask the patient to turn their head slightly away when treating the upper right facial surfaces, and for the anterior facials, ask the patient to

turn their head toward you. Sidesit ting in the 8-9 o’clock position is one of the most damaging positions the hygienist can assume, and should be eliminated or minimized to avoid injury. This can lead to pain and musculoskeletal disorders

in the hips, back, shoulders, neck and arms. Always try to face the patient directly during treatment. A saddle stool can help greatly with gaining close proximity in the 8-9 o’clock position. (Fig. 2)

A majority of the upper arch should be treated from the 11-1 o’clock positions, using direct or indirect vision. Mirrors should be used whenever direct viewing of the oral cavity requires leaving neutral posture. One study revealed that more pain-free dentists use a mirror than those who did not utilize a mirror.18 Frequent positioning at the 10 o’clock position without a mirror tends to encourage more arm abduction and neck/shoulder problems.19 The hygienist must remember to re-position the delivery system when moving around the head of the patient. Handpieces and instruments should be at about elbow level. Finger fulcrums are important to increase stability and to reduce compression in the carpal tunnel. Fig. 2 Sidesitting in the 9 o’clock position is one of the most damaging postures the hygienist can assume. A saddle stool will help with maintaining healthy posture and close proximity in the 9 o’clock position.

As the hygienist moves around the patient, the over head must be re-positioned to prevent shadowing. The light should parallel the hygienist’s line of sight to within 15°. Thus, the light will be placed slightly behind and to one side of their head. To avoid repeated upward reaching for the light, the hygienist should consider a lightweight head-mounted light, which will parallel even more closely with the operator’s line of sight to prevent shadowing.20

Fig. 1A

Fig. 1B

Fig. 2

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(Fig 3) 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.

Fig 3 Lighting should parallel the operator’s line of sight as closely as possible to prevent shadowing. Overhead vs. head-mounted light shown. Head-mounted lighting will cause the least shadowing. (Photo ©2010 from “Positioning for Success” DVD)

When treating the lower arch, adjust the headrest so the occlusal plane of the lower arch is about 30° elevated from the horizontal plane. (Fig 1B) On a double-articulating headrest, angle the head rest slightly forward, so the patient’s

chin tilts downward. On flat headrests, reverse the position of a contoured dental cushion, so the large end is behind the head. It may be necessary to slightly lower the height of the patient chair so forearms are parallel to the floor or sloping 10° upward.

Some hygienists may find that the chair does not adjust low enough to allow proper, relaxed arm posture. In this case, a saddle stool may be used to raise the hygienist to a higher seated position, since this places them between standing and sit ting.

The hygienist should watch their wrist as they move to dif ferent quadrants to ensure a safe, neutral wrist posture. If the wrist is excessively flexed, a dif ferent clock position should be explored to enable a straight wrist posture.

With tight patient schedules, emergencies and productivity goals to consider, it is easy to overlook proper patient positioning. However, taking the time to position the patient, hygienist 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.

Fig. 3

This article is based on Ms. Valachi’s new educational DVD, “Positioning for Success in Dentistry: Essential Ergonomic Guidelines for the Dental Team” . Hygienists can earn 2 CEUs with the DVD, which also contains assistant, dentist, loupes and wheelchair positioning techniques. The DVD, downloadable tests, as well as demo video clips are available on her website at www.posturedontics.com. Faculty and student discounts are available.

This article has been reprinted with the permission of Bethany Valachi, PT, MS, CEAS and RDH Magazine.

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Bethany Valachi, PT, MS, CEASis a physical therapist whose career took an abrupt detour af ter marrying a dentist with chronic low back pain. She now works full time as a dental ergonomic speaker/consultant and is founder and CEO of Posturedontics, a company that provides research-based dental ergonomic education and evaluates dental products. Bethany is clinical instructor of ergonomics at OHSU School of Dentistry in Portland, OR, and has provided expertise on dental ergonomics to faculty and students at numerous dental universities and hygiene schools, including faculty training at New York University College of Dentistry. As a certified ergonomic assessment specialist, she also consults with practicing dental professionals to improve ergonomics, work more comfortably and extend their careers.

Bethany is author of the book, “Practice Dentistry Pain-Free: Evidence-based Strategies to Prevent Pain & Extend Your Career”. A member of the National Speaker’s Association, Bethany has been invited to lecture at more than 250 dental meetings and was invited to speak at the 2009 International Dental Ergonomics Congress in Krakow, Poland. She has published more than 50 articles in the JADA, Australian Dental Practice, Dentistry Today, Dental Economics, CDA Journal, RDH, Contemporary Oral Hygiene and other peer-reviewed journals. Bethany is the author of the ADAA Ergonomic Home Study course and has produced dental ergonomic videos specifically for dental professionals.

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Bethany welcomes comments and may be contacted at bvalachi@posturedontics.com

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