The solution to challenging dental ergonomics

By Sanna Hakala, M.Sc., Physiotherapist

It has been both scientifically proven and experimentally shown that dental work is ergonomically challenging. Yet, the ergonomics can be at high level, if attention is paid on the environment and how the environment is used.

Dental workers often suffer from musculoskeletal disorders (MSD), and 90% of the early retirements caused by MSDs are work-related. Awkward postures, which are typically static and long lasting, are the main reasons of painful conditions.

When it comes to ergonomics, it is most important to remember that it is highly beneficial to avoid bending over the patient and rotating the body. Many dentists are used to work from beside the patient, which forces the body to an extremely uncomfortable position. Therefore working so that the patient is right in front of the dentist, would be recommended whenever reasonable. If the work needs to be done from the side, to minimise the bending and rotating, the head of the patient can be rotated towards the dentist. 

Bending and rotation of the body should be avoided as often as possible.

Pay attention to your sitting position

As most of the dentists sit while working, the attention should be paid on sitting ergonomics, because having a good posture in the upper body requires the correct setting of pelvis. Think of a tower; if one of the floors collapse, the whole tower from that floor up is out of balance. So if the pelvis is not positioned correctly, having good upper body posture is impossible.

The unbalanced posture stresses all the tissues in our body, as muscles, bones and ligaments are working outside their comfort zone, and that causes pain. The basis of our sitting posture is the position of our pelvis. Maintaining the good position of the pelvis while keeping the feet in front would require more strength from the hip flexor muscles than they can produce. Further, the bony structure of hip joints makes that position impossible. As a conclusion, sitting feet in front disables the correct positioning of pelvis, and forces the body to slouch.

Cartilages already start to age in our 20s

Other musculoskeletal conditions that results from long term passive sitting are joint problems. A cartilage, that covers the bony surfaces of the joint as a protection, doesn't have sufficient blood circulation. Instead, the metabolism of joints is based on “sponge-effect”: when the joint is loaded, the nutritional liquids squeeze out from the cartilage, and when unloaded the liquids squeeze in. When the joint is either unloaded or loaded in a stable position for a long time, the metabolism decreases, which fastens the process of degeneration.

In a slouched position where the back is rounded the structures that maintain the posture cannot function properly. Facet joints are open when the back is rounded (picture on the right).

Other sitting-related disorders

Other problems in sitting are less familiar but more fatal than MSDs. Flexed hip joints compress the groin area, disturbing blood circulation, especially in the veins that take the blood back up from the distal parts of the lower limbs. Disturbed flow in the lymph channels causes swelling. Together these two increase the risk of embolism that is the reason for many fatal conditions.

The slouched position of the upper body disturbs the digestive system because it inhibits peristaltics by compressing the intestine. Slouching disturbs also breathing, as the flexed thoracic spine blocks the costal ribcage, and prevents lungs from enlarging while inhaling. Reduced oxygen intake causes tiredness.

Constant pressure to the pelvic area disturbs blood circulation and compresses nerves, causing numbness that may result in problems in the intimate life of both men and women, because of the decreased sensation in the genital area. Because of the pressure it causes, sitting has been proven to be a risk for prostate problems, such as cancer. Also incontinence can be considered as a sitting-related disorder.

High sitting position opens the hip and knee joints to 135 degrees, which lets circulation flow freely.

Active sitting on a saddle chair provides good posture, health and energy

Sitting has an enormous effect on wellbeing, quality of life, and also the life expectancy. Sitting higher to open the circulation channels, loading the joints to promote joint health, positioning the pelvis in a way that the spinal curves are neutral, and having no pressure on the pelvic floor, are all enabled by a saddle chair with a divided seat. In dental care, saddle-type sitting enables working closer to the assistant or dentist, when the feet are at the sides and not taking space in the front. Also, the saddle chair enables working closer to the patient, so there is no need to bend over.

Saddle chair with a divided seat enables the correct setting of pelvis, which automatically results in a good posture. In addition, hip and knee flexion angles of 135 degrees are proven to be optimal for joint health.

Sitting feet on the side allows the pelvis to be set up correctly. It is essential that the saddle chair has a gap in the middle, i.e. that it is divided, otherwise the correct position of the pelvis is too uncomfortable to get and maintain because of the pressure on the pelvic floor. 

As the pelvis is slightly rotated forward on a saddle chair, the spine automatically has its neutral curves, discs are evenly loaded which prevents prolapses, and the big muscles don't need to work to maintain the balance. When the big muscles are not working, the core muscles can activate, and in a balanced position they do activate automatically.

Choose energy and wellbeing instead of health risks

Higher sitting position opens the hip and knee joints to 135 degrees, which is proven to be optimal for the joint health and also enables the correct setting of pelvis. In addition, when sitting on a saddle chair, the important sponge-effect helps the joints to maintain metabolism on a good level. The joints are not stiff even after long periods of sitting on a saddle chair. The wide angle of hip joints also allows circulation to flow freely. The lower limbs are not swollen at the end of the day, and the risk of a fatal embolism has decreased.

Good position of the upper body allows the digestive system to work properly, and breathing becomes easier. Well-functioning digestion and free breathing mean a more energetic feeling without headaches or constipation.