Temporomandibular Joint-Anatomy And Movement Disorders

Abstract

We know that when the mouth is closed or slightly open the head of the mandible lies in the articular fossa. In this position anatomically joint is stable and a blow on the chin causes fracture of the mandible rather than its dislocation. Posterior dislocation is also prevented by the strong lateral temporomandibular ligament. When the mouth is opened wide the head of mandible moves forwards and comes to lie just below the articular tubercle. This is the position in which Temporomandibular joint is highly unstable .A blow on the chin or even sudden opening of the mouth as in yawning can cause the head of the mandible to slip forward to the front of the articular tubercle. Once the joint is thus dislocated the mouth cannot be closed and this is known as locking of jaw in open condition. To reduce this dislocation the surgeon inserts both his thumbs into the mouth and exerts downward pressure on the lower molar teeth, simultaneously the mandible is pressed backwards. Generally this happens after an injury and leads to painful jaw movements along with clicking sounds during opening and closing of mouth. Temporomandibular Joints are foundations for dentistry, orthodontics and orthognathic surgery. If Temporomandibular Joints are not stable and healthy, there will be problem related to stability, occlusion, function and pain . 

As we open the jaws, the condoyle normally comes forward, the fascia and the disc moves forward with it because it is attached to the ligament that is attached to the back the condyle, around the front and all along the sides. It secures the disc to the condyle. The most common thing we see in the Temporomandibular Joints problem is the disc slipping anteriorly, posterior, backward or laterally. But the most common shifting is in the anterior direction. Here we see the disc fold a little bit which cause pain because the patient is pressing on the bilaminal tissue in the centre but there is no pain or inflammation as there are no blood vessels. This may not make any noise because the mandible is already in contact with the bad part of the disc and may not make it forward to make noise so this is a silent joint but a displaced disc. The other is little more involved, here condyle and the articular disc is little bit forward which does not click and pop when this patient open because the condyle will come over the back end of the disc, if it does not click and pop and is stuck behind here, then it is called a closed lock. It gets trapped behind that disc and the patient can't open his/her mouth very wide. In another case the disc is anteriorly displaced out in front. On opening the condyle comes forward but the disc remains anteriorly displaced. This is an anteriorly displaced disc without reduction. In this there may or may not be pain, it won't make any noise. We see this in a number of disease entities.