What goes wrong with dentists?  Pt 2

Prolonged sitting in the ‘head--forward position’ as described last month, tends to have a number of negative outcomes.  Even for a dentist sitting in the optimal position, more than half of the body’s muscles are statically contracted and there is very little movement of the vertebral joints.  This may result in small physiological changes that can lead to back, neck and shoulder pain or musculoskeletal disorders.

To re-cap:  when standing, your spine has four natural curves when viewed from the side: cervical lordosis, thoracic kyphosis, lumbar lordosis and sacral kyphosis.  These curves are inter-dependent: a change in one curve will cause a curve above or below it.  The sacral curve comprises  five fused vertebra, so its movement is very limited.  The other three curves, especially the lumbar and cervical, are more mobile and and can be influenced more easily.  When the curves of the spine are normal and balanced against gravity, the spine is mostly supported by the bony structures of the vertebra resting on top of each other.  When any of these curves becomes exaggerated or flattened, the spine, in order to stay erect, must increase its dependence on surrounding muscles, ligaments and soft tissues.

Sit unsupported for extended periods, as dentists often do,  and your lumbar lordosis flattens and your spine relies on the local muscles and soft tissues to keep it upright.  This causes tension in these structures, leading to back strain and trigger points (q.v.) and  pressure on the discs.

Likewise, cervical lordosis is common among dentists - the ‘head-forward posture’ described last month.  Years of holding your head and neck in an unbalanced forward posture to gain maximum visibility during treatment means that the muscles of the cervical and upper thoracic spine must contract constantly to support the weight of your head. This can result in headaches, chronic neck pain, shoulder and inter-scapular muscle pain and may radiate into the arms.  This can cause weakening of the cervical discs and possible degeneration and herniation.  The muscle imbalances of head forward posture eventually contribute to a rounded shoulder posture and loss of height (check out your friends and colleagues).  This in turn can predispose to rotator cuff impingement when reaching out for instruments etc.  Keeping your arms held static in an elevated or abducted state of greater than 30 degrees impedes the blood flow to the shoulder muscles and can also cause ‘trapezius myalgia’, a fancy name for that chronic, often burning, deep pain in the upper trapezius that you may  be familiar with.

An extensive literature review by a dentist and physiotherapist in the JADA (2003) (1) outlines a number of helpful strategies for minimising musculo-skeletal problems resulting from work position.  I will summarise them briefly here.  For more detail, the article is available on the net.

1.     Maintain your lower back curve

• tilt your chair seat forward 5-15 degrees.  This will place your hips slightly higher than your knees.  If you are not used to this position, start with a few degrees of tilt and gradually increase it
• make sure that your feet are firmly planted on the floor.
• sit close to the patient and put your knees under their chair, if possible
• use the lumbar support on your chair as much as possible by adjusting it forward to have contact with your lower back
• regularly promote lumbar stabilisation throughout the day by contracting your transverse abdominal muscles.  To do this, sit tall with a slight curve in your lower back, exhale, pull your belly button towards your spine without letting the back curve flatten. Hold the contraction while you inhale and exhale.

2.     Pivot forward from your hips, not your waist

--Try to stabilise your lumbar curve by doing the above manoeuvre before you pivot.  This will take practice, but eventually it will become automatic.

--avoid twisting as much as possible; have your instrument delivery system over the patient rather than behind you or to your side, to minimise twisting.  If you must twist to retrieve instruments, swivel your chair and retrieve the object with the closest hand.

3.     Use proper magnification.

• The declination angle of your scope should allow you to maintain less than 20 degrees of neck flexion  (more than 20 degrees causes increased neck pain)
• your working distance should allow you to have your elbows close to your sides and your shoulders relaxed
• Magnification of x2 is recommended as it gives enhanced visual detail without a huge decrease in the size of your visual field.
•  

4.     Know how to adjust your chair

-just buying an ergonomic chair is not enough, you need to be fully au fait with how to fit it to your needs. Many chair dealers will allow you to have an in-office trail before you make a decision

-trialling a saddle chair may be worth while, but they don’t suit everyone

-try to adjust your own  chair before you position your patient

-alternate between sitting and standing, as this allows you to use different muscle groups.

-reposition your feet throughout the day: subtle changes in your foot position shift the workload  between muscle groups

-don’t position your patient too high.  This causes you to elevate your shoulders and abduct your arms, causing prolonged static neck and shoulder tension.  Your elbows should be close to your sides and your forearms approximately parallel with the floor.

-as a general rule, the patient should be in the semi-supine position for mandibular procedures and in the supine position for maxillary procedures.

5.     Take regular breaks

Frequent  ‘micro-breaks’ of up to 60 seconds  have been found to be more beneficial than longer, less frequent breaks.  However, the tendency with four-handed dentistry is to work for longer uninterrupted periods, so this will take discipline on your part. If the rest periods are too far apart, the rate of damage to muscles will exceed the rate of repair, eventually resulting in breakdown of tissue.Stretching works by increasing local blood flow and stimulating the joints to produce synovial fluid.

Economic cost-effectiveness of varying lengths of micro-breaks has actually been extensivly studied.  The addition of 30-second micro breaks increases productivity and decreases discomfort.  Micro breaks can be taken while you wait for an anaesthetic to work or during a procedure without interrupting your work flow. Use the work breaks to stretch in the direction opposite to the one you have been static in; when at home do both sides. The Brugger Stretch (last month) is a useful one to do in the surgery.

 A number of stretches specific to dentists are shownin Fig 1.

To stretch effectively, get into the starting position and exhale as you increase the intensity of the stretch up to a point of mild discomfort or tension.  Hold the stretch for 2-4 breath cycles.   You will need to discipline yourself to do these; Many people find stretches tedious, especially men, as they often don’t find them easy or rewarding. Persist and you will notice an improvement in days; after a month your posture will be improved, and you will be helping to prevent long term deterioration. 

Trigger points: if you have pain that is aggravated rather than relieved by stretching, you may have developed a ‘trigger point’.  This is caused by a sustained contraction in a tight band of muscle.  It feels like a hard knot;  when pressed firmly it hurts , and pain may be referred to another area.  Trigger points prevent the surrounding muscle fibres  from contracting  or relaxing, therefore they decrease flexibility and reduce blood flow to the area.  You need to release them as promptly as possible, and you can do this to a certain extent yourself. Wedge a tennis ball between your back and a wall and rub around the area and press on the point.  If you have a trigger point lower down your back, lie on the floor and do the same thing. (This usually elicits groans of pleasure) Better still, go to see a  a chiropractor or physio. trained in trigger point therapy.  Musculoskeletal physicians are another alternative; they are trained in trigger point injection or a technique known as ‘spray and stretch’.

Strength exercises are also important to avoid musculo- skeletal disorders.  Dental surgeons should concentrate on the trunk stabilizer muscles and the shoulder girdle, especially the middle and lower trapezius and the downward gliding muscles of the rotator cuff.  Avoid over-training the chest and anterior neck muscles, deltoids and upped trapezius as these can exacerbate muscle imbalances.  Arnold Swartznegger- type physiques are unsuited to dentistry.  Stretch the chest, hamstrings, low back, buttocks and hip flexors, and try to do aerobic exercise for 20 minutes three times per week to keep muscles healthy and capable of withstanding insult.

An American dentist has  developed a ‘Powerposture’ daily exercise program for dentists, which he claims takes just 10-15 minutes per day.  I have not seen it, but it is available from www.powerposture.com.  A lot of what I have said here applies to any job which involves long periods of sitting.  Apparently, 15 minutes is enough to start deleterious muscle changes, so children who play computer games for hours on end are especially at risk.  Fifteen minutes of targeted muscle movement per day would seem a good investment.  As one  researcher concluded, “all the years of training, the skill acquisition and capital investment are worth nothing if you can’t hold up to the physical demands of dental practice and then retire healthfully”. Sobering indeed.

References: 1. Valachi,B & Valachi,K JADA, Vol 134, No12,1604-1612

                     2. Valachi,B & Valachi,K JADA, Vol 134, No10,1344-1350

                        3.Christman,J Barcelona Orthodontic meeting, 03/2003. see www.powerposture.com/barcelona

(With thanks to Dr Adam Meredith for additional information: www.spineandhealth.com.au)