NEUROMUSCULAR DENTISTRY AND CRANIOMANDIBULAR DISORDERS

IMI Clinic

The temporomandibular joint (TMJ) is an articulation defined “by movement”: it connects the jaw to the skull, and enables chewing, swallowing and mimic movements. During mastication, the muscles allow the movement of the jaw in the three spatial dimensions.

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The TMJ consists of the mandibular condyle (the section of the lower jaw bone that connects with the skull) and the glenoid fossa of the temporal bone. A disk (or articular meniscus) sits between the two which delimits the joint cavities thereby enclosing the synovial liquid and acting as an anchoring point for the muscular insertions.

In normal conditions, the movement of opening the mouth occurs when the condyle rotates and slides forwards and the disk adhering to the head of the condyle itself move simultaneously. However, pathological conditions may exist, such as malocclusions (the incorrect positioning of the teeth), altering the functioning of the muscles, and pathological processes involving the condyle itself.These are capable of causing joint or muscle-type dysfunctions of the TMJ. Such dysfunctions of the TMJ are known as temporomandibular dysfunctions (TMDs).

The symptoms of temporomandibular dysfunctions

There are three symptoms that act as a guide for diagnosing TMDs:

  • Pain in the masticatory muscles in the pre-auricular region.
  • Limitations or alterations to the normal muscle functions.
  • Joint noises (clicking).

There are secondary symptoms that are also important and must be checked:

  • Dizziness;
  • Headaches;
  • Diffused facial pain.

Temporomandibular dysfunctions

TMDs can be divided into three distinct, internationally classified categories:

  • Muscle disorders, such as the “open clock”: the patient is not able to close their mouth and it remains open in the yawn position. Prolonged contractions or tension in the masticatory muscles are also classed as muscle disorders
  • Joint disorders, such as a clicking noise on opening the mouth, difficulty eating or talking, headaches, earache.
  • Disorders atbone-level such as hypoplasia excessive underdevelopment of the organ, and therefore underdevelopment of the condyle itself.

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As far as the muscle disorders are concerned, local muscle pain may be associated with increased rigidity (tension) of the muscles, inducing the myofascial syndrome. This causes constant pain in the muscles that are adjacent to the painful areas. It can also be caused by myospasms (abrupt and sudden muscle contractions).

The myospasms can  determine a blocked jaw movement; otherwise the muscle pain may be linked to myalgia, constant pain affecting a specific muscle.

The treatment mainly focuses on muscle exercises carried out with intra and extra-oral manoeuvres. Nevertheless, it is very important to teach the patients how to control his/her movements.

Joint disorders are instead due to anterior dislocation of the disk, meaning that the capsular structures are no longer contained inside the glenoid fossa, with subsequent pressure and a double clicking noise. In this case the pain is absent and there is no asymmetry or limitation to the movements.
There are two types of dislocation of the disk – with or without reduction.

In the first case there will be loss of contact between the condyle and the disk which triggers a permanent condition involving the anterior dislocation of the disk. During the mouth opening movements there will be a clicking noise that disappears upon closing the mouth. As far as dislocation without reduction is concerned, it is important to divide this into two subtypes: acute and chronic.

Acute dislocation without reduction

In acute dislocation, the movement is limited because the disk prevents the translation movement of the condyle.

Chronic dislocation without reduction

Instead, in the chronic form, the condyle recovers a limited amount of its translation movement while compressing the disk further forwards. The patient may experience mild pain (due to a sudden block when closing their mouth), but an X-ray will reveal whether this has caused joint arthrosis.

In dislocation with reduction, relaxation and lengthening can be observed, especially in the capsular zone. It is important for the operator to carry out muscle relaxation manoeuvres by placing their thumb on the patient’s molars and pushing downwards.

In the instance of dislocation without reduction, the treatment is very similar to that of dislocation with reduction whereby the stretching of the capsule and traction of the condyle will be carried out by exerting greater force and for a longer time. Most importantly, as already mentioned, it is essential to teach the patient how to carry out daily physiotherapy exercises.

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