Risk Factors that Contribute to MSDs

The dental professional is exposed to a multitude of risk factors that can contribute to MSDs. The primary factors include: repetition, force, mechanical stresses, posture, vibration, cold temperature and extrinsic stress. Of these, posture is one of the most frequently cited risk factors in dentistry.13-15

Postural stress occurs with strained sitting positions, such as those associated with bending/slouching, head tilting, torso twisting, tipping shoulders, and raising elbows outside the normal range of motion.14 These risk factors may work alone or in concert with one another to compound the problem and/or further expose one’s own vulnerability earlier than later. The obvious risk factors include sitting, compounded by prolonged sitting, and awkward positioning. The following briefly captures what researchers have found concerning these risk factors.

While there is a very low level of muscle activity during sitting as compared to dynamic activities, there is a 35-40% increase in intra-discal pressure as compared to standing16 making pain an inevitable experience for those who engage in prolonged static sitting.

Prolonged Sitting
The inactivity associated with sitting may cause fatigue as well as injury. Inactivity can cause a build up of metabolites that can contribute to disc degeneration and disc herniation in both the cervical and lumbar spines. Additionally, in sitting, the lack of motion statically loads muscle, ligament, and joint tissue (passive tissue forces), which can accelerate disc degeneration and increase the risk of herniation.17

Awkward Positioning
Cervical flexion during prolonged positioning can cause an increase in disc pressure and an increase in muscular tension. Correspondingly, there is an increase in tension on the spinal cord, brain stem, and the nerve roots.18 Keep in mind that the position of the thoracic spine drives the position of the head. If the thoracic spine is more flexed, the result is an increase in lower cervical flexion potentially causing both pain and pathology.19

Additionally, in the slouched position, there is backward rotation of the pelvis causing flexion of the spine with resultant widening of the lumbar intervertebral discs and strain on the lumbar ligaments.20 Other less obvious risk factors dental professionals may encounter that can lead to MSDs include:

  1. Fatigue
  2. Altered Spinal Curves (even when not in awkward positions)
  3. Lack of upper extremity support (intrinsic or extrinsic)
  4. Poor level of fitness (flexibility, strength and endurance)
  5. Lack of adjustable equipment
  6. Poor lighting/vision
  7. Environmental stress: The stress of the dental environment also plays a role in triggering physical abnormalities that contribute to pain. Marras et al demonstrated that increased environmental stress while sitting actually caused an increase in compression and shear in the lumbar spine21 with pain as on obvious outcome.

Be reasonably au fait with these risk factors. Familiarity and understanding are the first steps in reducing the risks of MSDs. The remainder of this course directs the reader to understand their body’s apposite anatomy and potentials for pathology, and suggests positions and movements to minimize the impact of MSDs. Recommendations of fitness activities for maintaining the health specifically related to dental professionals is covered in Practice in Motion: Part II - 6 Components of Posture.