February 1, 2009
by Oral Health
In recent years, musculoskeletal disorders (MSD) have become epidemic. At any one time 85% of the population experiences low back pain (LBP).1 It has become the number two reason for doctor visits, and that doesn’t include the many patients that don’t seek advice, just hoping “it would go away.”
The nature of the dental profession and the many positions that are incurred during an average work day by the practitioner, has a huge impact on the body, and it carries with it a high prevalence for MSD. In a recent research article looking at dentists in Greece, 46% suffered from chronic LBP, with 25% being of a severe nature. 3 In fact, those with LBP also reported having either neck pain, 41% of the time, or hand and wrist pain 38% of the time. 3 In fact, 35% of the time there are usually two MSD that are having an impact on a dentist at any one particular time. 3 These MSD can become very debilitating and can affect the quality of life of for the dental professional. The effects of MSD will manifest themselves not only in decreased work, but maybe, as importantly, the time spent with family and/or during personal time. Although we rarely miss work due to the MSD, (16%). It is more likely to lead to severe disability and a subsequent impact on the quality of life. In fact, the most common complaint amongst dentists is how MSD is impacting their personal life, and the lack of time between working periods for recovery. 4
That being said, there is a direct relationship between decreased fitness levels and MSD. Musculoskeletal disorders arise from a number of sources, however the primary cause in the dental practice is the prolonged static posture (PSP’s). With PSP’s, neuronal ailments, ischemia and trigger points, disc herniation/bulging, and spasticity will develop. These are all due to the common dental posture; seated with a forward lean, lateral neck flexion with rotation and arm abducted.
In this article a close look will be taken at PSP’s, and how they arise, as well as methods to combat it in the work place. In a follow up article, preventive and rehabilitative exercises will be discussed that can be incorporated into exercise workout routines to increase health, quality of life, and the resultant increased energy and productivity that will come with that.
As a dentist, the level of precision and control is quite high, having to look into someone’s mouth, and to work with fine tools in a confined space for long periods of time. It is the required level of control and accuracy, that requires the dental professional to maintain a rather controlled and static posture for these extended periods of time. Although we have muscles in our bodies that are meant to maintain postural positions, humans have yet to evolve to the point where the muscles can work effectively without some rest. Physiologically, a sustained tension on a muscle or any soft tissue for extended periods of time without rest causes ischemia and may lead to necrosis within the muscle. 5 This can only be remedied with periods of rest, and that can be done in a number of ways, all to be discussed later in this article.
What complicates and increases the risk of injury is the forward lean at the waist and head carriage commonly found in the dental posture. This position, when maintained for long periods of time will eventually lead to the muscles “shutting off ” thereby relaxing the stabilizing muscle structures of the spine.
To make sure we don’t “fall apart,” the ligamentous structures take the brunt of the load. This can only be sustained for so long before the ligamentous tissues tear, however before this happens, creep occurs.
The gradual deformation of the intervertebral joint under constant load, constitutes creep, and it effects the ligaments. In unsupported sitting, compressional loads in the lumbar spinal disks increases 40% above normal forces compared to those loads incured during standing. During forward flexion and rotation, a position often assumed by dental operators, the pressure increases 400%, making the structure susceptible to injury. 2
This pressure, or load, on the ligament stretches it. The body has the ability to restore itself to its original length, however when this position and action is repeated multiple times, restoration of the initial length of a ligament occurs at a lesser rate and to a lesser extent than did the deformation. 1 This creates a new set point, where the final resting length of the ligament is greater than its original, allowing for less stability of the intervertebral disc, and more mobility, so that all it takes is a simple motion like bending to pick up a pencil to cause serious harm. This phenomenon occurs at all vertebral segments, but most predominately at L4-L5, L5-S1 disc spaces in the low back, as well as C2-3 and C5-6 in the neck. 2
These are the areas where disc herniations most commonly arise from. However the signs, aren’t always immediately manifested. When it is noticed, often nothing is done about it. Once the ultimate bad news of a disc herniation does occur, it can be a big blow that can put someone out of commission for many months. The common neurological signs and symptoms seen and felt in the hips and legs and in particular down the arm into the hands should be a red alert signal that something needs to be looked at and taken care of. This is the worst case scenario. However, it is one that does occur, and occurs often. In fact ap proximately 5% of all LBP is from a herniated disc. 5
While we need to adjust to our already existing seated postures it is important to understand that while there will be huge improvements with an upright alignment in our sitting posture, ultimately you will need to know that there isn’t one ideal sitting position. Any, prolonged static posture wears on the structures involved, even an upright posture.
In Figure 2, you can see that the spinal alignment is in neutral, and there isn’t any creep nor excessive bending or twisting. However, the muscular involvement can only be maintained its activity so long before there is tissue damage from CO2 build up. 2 Trigger points and necrosis can also occur in this manner. So, although improvement may be made to lower back and neck health with an upright posture, and is far less detrimental to your health than the common static posture of dentists, it is still not the most ideal position.
Here is where we get a little radical, understanding there is no ideal seated posture or positioning. In any position there are always structures that are taking more load, than others. Therefore, muscles and ligaments are always in a compromised exposed position. What may work most effectively is to frequently alter your seated posture and position. Although you may have the temptation to sit upright and to avoid excessive bending and twisting, it is important to get up and move around, and allow the load bearing structures to have the opportunity to recover. In some practices this is easily done by moving from patient to patient, however there does come a time when extended periods of time will be spent with one patient. It is at these times that upright posture and changing of positions will serve the dental professional quite well.
Through the years, an evolution in equipment has created a freedom for the dental professional, however due to the nature of the profession, LBP has an ever increasing prevalence. The truth is that most of your day is spent at work, so the steps you take while at work can go along way to improving your longevity as a dental professional, as well as the quality in which you live your life.
The next article of this series will discuss exercises that can be done to rehabilitate existing MSD and more importantly prevent them from occurring.
Mahmoud Zaerian graduated from York University with an honours degree in Kinesiology. He is currently studying at the Canadian Memorial Chiropractic Colle
ge in pursuit of his doctrine in Chiropractics. Over the last nine years, Mahmoud has worked with some of the Toronto’s top amateur athletes, and Canada’s Olympic team. http://focusitc.ca/
Oral Health welcomes this original article.
1. Valachi, K and Bethany Valachi, Mechanisms leading to musculoskeletal disorders in dentistry. Journal of American Dental Association, Vol. 134, No 10, 1344-1350.
2. Evangelos C Alexopouls, Ioanna-Chrisina Stathi, and Fotini Charizani, prevalence of musculoskeletal disorders in dentists. BMC Musculoskeletal Disorder,. 2004; 5:16.
3. Karasek R, Brisson C, Kawakami N, Houtman I, Bongers P, Amick B. The job content questionnaire (JCQ): an instrument for internationally comparative assessments of psychosocial job characteristics. Journal of Occupational Health Psychology. 1998; 3:322-355. doi:10.1037//1076-89188.8.131.522.
4. Fish DR, Morris-Allen DM. Musculoskeletal disorders in dentists. NY State Dent J. 1998; 64: 44-48.
5. CMCC 2007 Course ware. Dr. Guerreiro.
6. Anderson GBJ. Epidemiological features of chronic low back pain Lancet. 1999; 354:581-5. doi: 10. 1016/ S0140-6736 (99) 01312-4.
7. Panjabi MM, Tech D, White AA. Basic biomechanics of the spine. Neurosurgery 1980; 7:76-93
35% of the time there are usually two MSD that are having an impact on a dentist at any one particular time
Approximately 5% of all LBP is from a herniated disc
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