Part 2: Consequences of poor ergonomics amongst dental hygienists
By Becca Scarratt (Physiotherapist, www.cliniquephysiobecca.ca, FB, LinkedIn)
Prevalence and risk factors of Work-related musculoskeletal disorders (WMSDs)
Due to postural demands of static positioning and awkward postures, dental hygiene professionals are at high risk for developing work-related musculoskeletal disorders (WMSDs) specifically in their wrists and hands (60-69.5%); neck (54-83%), shoulders (35-76%) and lower back (Parsons 2019, Partido 2017, Morse 2010, Hayes 2009).
Risk factors of WMSDs with specific reference to dental hygiene include: poor flexibility, improper positioning, infrequent breaks, repetitive movements, weak postural muscles, prolonged awkward postures and improper adjustment of equipment (Gupta 2011).
I will present three common injuries related to poor ergonomics for dental hygienists: eyestrain, tech-neck and carpal tunnel syndrome (CTS).
The most common causes of eye strain include: looking at digital device screens; reading or looking at dental mirrors without pausing to rest your eyes; being exposed to bright light or glare; straining to see in very dim light and of course driving long distances and doing other activities involving extended focus. Eyestrain signs and symptoms include: sore, tired, burning or itching eyes; watery or dry eyes; blurred or double vision; headache, sore neck, shoulders, and/or back; difficulty concentrating; or feeling that you cannot keep your eyes open. During the work day dental hygienist are encouraged to take a pause. The GOLDEN RULE in ergonomics is the rule 20-20-20. That is to say each 20 minutes take a 20 second break and look 20 feet away. During the 20 second pause why not try a few eye exercises such as The Box. For The Box eye exercise first move your eyes horizontally three times to the right and to the left without moving your neck or head. Next close your eyes for 5 seconds. Then move your eyes up and down three times and then close your eyes a second time for 5 seconds. Finally move your eyes first clockwise three times and then counterclockwise 3 times and finish by closing your eyes for a last 5 seconds. During The Box the times that you close your eyes for 5 seconds it is even more relaxing to place the heel of your hands over your eye sockets.
Tech-neck is officially the act of holding your head flexed and forward while looking down at your hand-held device or laptop screen. This neck posture is seen all too often among dental hygienists who have a forward head posture instead of using their eyes to look downwards into their dental mirror. As is evident from the name tech-neck puts your cervical spine in a tenuous position. This so-called forward head posture increases the force on the cervical spine. The average adult head weighs 4-5kg which when aligned is supported by the bony structures, muscles, ligaments, and tendons of the neck. With forward head posture where the ear of the head and neck are anterior to the midline of the shoulder; each 1cm of forward head posture is equivalent to 6kg of weight on the spine (Kocur et al 2019) Symptoms of tech-neck include head-ache, eye strain, stiff or painful neck, shoulder pain and thumb fatigue. What can you do to stop tech-neck? You can raise your phone to eye level so that your neck does not have to be tilted; look downwards with your eyes instead of compromising your neck posture; take frequent breaks away from forward head posture ; stand up; arch and stretch and stay fit. In dental hygiene you may not have your hand-held device or laptop screen with you but you are constantly looking into your dental mirror, often with the same forward head posture as one sees with tech-neck. Make sure while working that you use you look downwards with your eyes to look into your dental mirror and not using a nodding motion of the neck which becomes forward head posture. Also constantly reposition your chair around the correct clock positioning to easily visualize different sectors of the patient’s teeth while not compromising your posture. Remember that you can ask your patient to turn their head either towards you or away from you or lift their head upwards to accommodate viewing the different sectors of their teeth.
RSI (repetitive strain injury) Many cases of WMSDs among dental hygienists are related to cumulative trauma and are considered repetitive strain injuries (RSI) I.e. overuse. These RSI can include: Tech-neck (which I have already presented); deQuervain’s disease; carpal tunnel syndrome (CTS); rotator cuff tendinopathy; forearm tendinopathy; cervical radiculopathy; golfer,s elbow; or tennis elbow. The prevalence of RSI in adults is 5-10% but can go up to 40% (Pascarelli 1994) Those at high risk of getting RSI are those performing repetitive monotonous movements including: industrial or construction workers, athletes, musicians, desk workers, bus drivers, cleaners, cooks, and you our dental hygienists. But what causes RSI? Causes of RSI include: stressing the same muscles through repetition; the same posture for long periods; extended periods of time in an abnormal posture (eg. arms overhead; constant trunk flexion to same side); lifting heavy objects; using vibratory instruments and poor physical condition.
Dental hygienists are at increased risk for carpal tunnel syndrome (CTS) (18.4%) which is a RSI (Anton 2002, Harris 2020). CTS is the slowing of the median nerve on sensory nerve conduction study at the wrist with symptoms of numbness, tingling or pain in the median nerve distribution due to compression on the median nerve in the wrist (Lalumandier 2001). According to Butler (1995) RSI is multifactorial so one has to address posture, diet, sleep and stress. In physiotherapy our actions for RSI include R.I.C.E. (rest, ice, compression, elevation); splint; exercises; and stress reduction/relaxation training. Here is a diagram of median nerve exercises which often reverses the symptoms of CTS (Totten & Hunter 1991).
However some cases of RSI may require medical intervention in the form of NSAID medications, steroid injections, surgery. Suggestions for the prevention of CTS include: continually positioning your dental hygienists chair to optimize your work posture. For example move your chair to the head of the patient when working the sectors of the teeth most visible from there; adjust the height of the patient’s chair so that your thighs are under the patient’s chair and ensure that you are always working in close proximity to the patient. Secondly, when working with vibratory equipment try using forearm supports. And finally be fit!
In summary, exercise such as The Box, the Median nerve glides; frequent pauses during the work day using the Golden Rule 20-20-20; avoiding forward head posture by looking downwards with your eyes and constantly repositioning your chair in the clock position throughout treatment are some of the ergonomic factors which when followed may aid in the prevention and management of WMSDs among dental hygienists.
“Pause for a moment and become fully aware of how you are sitting/standing right now and ask yourself two questions:
1) Do I feel relaxed in my current posture?
2) Do I feel comfortable in my current posture?
If YES stay there; if not then move and change it!” B.Jam 2021
References Part 1 Ergonomics for dental hygienists
By Becca Scarratt (Physiotherapist, www.cliniquephysiobecca.ca, FB, LinkedIn)
Katzmarzyk PT, Church TS, Craig CL, Bouchard C. Sitting time and mortality from all causes, cardiovascular disease, and cancer. Med Sci Sports Exerc. 2009 May;41(5):998-1005
Hamilton MT, Hamilton DG, Zderic TW. Role of low energy expenditure and sitting in obesity, metabolic syndrome, type 2 diabetes and cardiovascular disease. Diabetes. 2007 Nov;56(11):2655-67
Slater D, Korakakis V, O’Sullivan P, Nolan D, O’Sullivan K. “Sit Up Straight”: Time to Re-evaluate. J. Orthop Sports Phys Ther. 2019 Aug;49(8):562-564
Vandyken C. Course webinar. Exercise reframed post course resources. 30 Sept 2021
Gupta S. Ergonomic applications to dental practice. Indian J Dent Res 2011 Nov-Dec;22(6):816-22
International Ergonomic Association (IEA) What is ergonomics-definition and domains of ergonomics www.iea.cc (Accessed Feb 2022)
Rucker LM, Sunell S. Ergonomic risk factors associated with clinical dentistry. J Calif Dent Assoc 2002;30(2):139-46
Rempel D, Lee DL, Dawson K, Loomer P. The effects of periodontal curette handle weight and diameter on arm pain: a four-month randomized controlled trial. J Amer Dent Assoc 2012;143(10):1105-13
Michalak-Turcotte C. A problem-solving approach to ergonomic intervention in dental hygiene Part 1. Dim of Dent Hyg 2005:3(9):18, 20-1
Morse T, Bruneau H, Michalak-Turcotte C, Sanders M, Warren N, Dussetschleger J, Diva U, Croteau M, Cherniak M. Musculoskeletal disorders of the neck and shoulder in dental hygienists and dental hygiene students. J Dent Hyg 2007;81(1):1-20
Rempel D, Lee DL, Dawson K, Loomer P. The effects of periodontal curette handle weight and diameter on arm pain: a four-month randomized controlled trial. J Amer Dent Assoc 2012;143(10):1105-13