Toxic or healthy seating

April 1, 2010
All too often, the selection of the stools in the clinical setting is determined by one or more of the following criteria ...

It’s your choice

by Anne Nugent Guignon, RDH, MPH
[email protected]

All too often, the selection of the stools in the clinical setting is determined by one or more of the following criteria:

  • The stool was already in the room when we joined the practice
  • It was picked to match the room décor
  • The operator stool was added as a freebie when the doctor built or remodeled the office

These reasons have nothing to do with ergonomics, workplace safety, or operator comfort. A clinician’s stool acquired for any one of these reasons rarely fits the user properly. In many cases, the stools may lead to health issues that can become chronic or even permanent.1-5 Many spend eight hours a day using an operator chair that does not fit, nor provide adequate whole body support.

Working in a dental office is hard. Tight time schedules, scared patients, and exacting procedures can make the day crazy. Add in a few late patients, a fidgety child, a sensitive patient, or equipment that breaks midprocedure, and it is easy to get tense and work with less than ideal postures — just to get through the day.4 Pressures like this make it more important than ever to use a clinical stool that promotes health rather than creating additional musculoskeletal stress.2,3.5,6

In the mid-1960s, sit-down dentistry became popular, and the first dental stools resembled stools used by physicians for brief five-minute exams — short, round seats without a back.1 Unlike physicians, dental professionals spend hours sitting; therefore, our clinician stools cannot be a one-size-fits-all design. We come in all sizes: short, tall, slim, chunky, long legs, short legs, and different torso lengths.

If the former basketball player Michael Jordan suddenly pursued a career as a hygienist, he would certainly need a different seating support system than a female actress such as Salma Hayek. Properly designed, clinician-specific seating creates the foundation for active, dynamic postures that support musculoskeletal health.1,3,5,6

Seats on dental stools come in a wide variety of shapes and sizes that include round, rectangular, trapezoid, contoured, bucket-shaped, and English or Western saddle designs, which allow a sit-stand position that is especially valuable where there is little room for the knees.1,7

Seat pan depth is critical. It must be large enough to support a clinician’s thighs and buttocks but shallow enough to allow a couple of inches between the edge and the back of the knees. A seat pan that is too deep creates dangerous leg impingement or forces the user to perch at the edge of the stool, eliminating any possibility of using the backrest. It is ideal to tilt the seat pan slightly so the back is an inch or so higher than the front, a position that reduces musculoskeletal stress and improves circulation.

Both saddle chairs and those designed with a sculpted-edge seat pan allow us to position close to the mouth without bumping into the patient chair. Seats with a smooth, rounded waterfall front improve circulation over chairs that have a seamed right-angle hard edge. Quality padding helps prevent pressure points and provides a more comfortable seating experience throughout the day.

Most chairs today feature some sort of backrest, which may or may not provide adequate lumbar support — a key to maintaining the natural s-curve in the lower back. Ideally, the backrest should be adjustable to fit the clinician’s lumbar area. Some lumbar support systems are manufactured to maintain contact with the back as the clinician moves the trunk of their body back and forth during the dental appointment.1-3,6,7,9

Armrests are just that, a place to rest one’s arms, not to support the weight of the entire torso. Armrests need to be adjustable, with the height and position set where the clinician’s shoulders and arms are supported in a relaxed position. Some armrests move as a clinician leans forward or back; others swing out of the way, and some remain fixed, according to a clinician’s physical specifications.1,10

Chair height is another essential component of healthy seating. Most of us were taught to sit with our thighs parallel to the floor, a dangerous posture that flattens out the natural curve of the lower back. To maintain an adequate curve in the lumbar spine, adjust the stool height so the hips are higher than the knees with the feet flat on the floor and in the case of a traditional flat seat, tilt the seat pan to create a slight downward slope from back to front.1,5,7

A chair can be considered ergonomic only if it fits the user correctly during a specific work activity. Your clinician stool should be a fundamental part of your personal comfort zone. If not, learn all you can about healthy operator seating, study the options, and create a plan to acquire a seating system that creates a healthy working environment for you! If that means purchasing your own stool, remember, you are worth the investment.


  1. Pheasant S, Haslegrave CM. Bodyspace: anthropometry, ergonomics, and the design of work. Bocca Raton: Taylor and Francis. 2006
  2. Watanabe S, Eguchi A, Kobara K, Ishida H. Influence of trunk muscle co-contraction on spinal curvature during sitting for desk work. Electromyogr Clin Neurophysiol. 2007 Sep;47(6):273-8.
  3. Makhsous M, Lin F, Hendrix RW, Hepler M, Zhang LQ. Sitting with adjustable ischial and back supports: biomechanical changes. Spine (Phila Pa 1976). 2003 Jun 1;28(11):1113-21; discussion 1121-2.
  4. Lis AM, Black KM, Korn H, Nordin M.Association between sitting and occupational LBP. Eur Spine J. 2007 Feb;16(2):283-98. Epub 2006 May 31.
  5. Mandal AC. Balanced sitting posture on forward sloping seat. Accessed at on February 8, 2010.
  6. Pope MH, Goh KL, Magnusson ML. Spine ergonomics. Annu Rev Biomed Eng. 2002;4:49-68. Epub 2002 Mar 22.
  7. Tiedeman J. New concepts in seating. Accessed at on February 7, 2010.
  8. Makhsous M, Lin F, Bankard J, Hendrix RW, Hepler M, Press J. Biomechanical effects of sitting with adjustable ischial and lumbar support on occupational low back pain: evaluation of sitting load and back muscle activity. BMC Musculoskelet Disord. 2009 Feb 5;10:17.
  9. Lord M, Small J M, et al. Lumbar lordosis: Effects of sitting and standing. Spine:1 November 1997. 22;21.
  10. Ernst E. Ergonomic aspects of sitting. Fortschr Med. 1992 Jan 20;110(1-2):29-30, 33.

Anne Nugent Guignon, RDH, MPH, is the senior consulting editor for RDH magazine. She is an international speaker who has published numerous articles and authored several textbook chapters. Her popular programs include ergonomics, patient comfort, burnout, and advanced diagnostics and therapeutics. Recipient of the 2004 Mentor of the Year Award, Anne is an ADHA member and has practiced clinical dental hygiene in Houston since 1971.

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