The TMJ(Temporomandibular Joint) is the only 3D joint in the human body that has both translational and rotational movements. Hence, any damage to the joint needs to be corrected holistically. Any surgical intervention should be attempted only if there is an ankylosis or trauma within the joint complex. The TMJ(Temporomandibular Joint) or the jaw joint is formed between the mobile condyle of the lower jaw (mandible) and fixed temporal bone of the skull. Any disturbance within the joint would end up as TMJD(Temporomandibular Joint Disorder).
There are several joints in the body. A joint is where two bones meet to allow smooth movement. To ensure this all joints would have a joint space within which a lubricating medium is present. Unlike, any other joint where synovial fluid acts as the medium but within the TMJ complex there is a cartilaginous tissue known as the articular disc. In and around this joint space transverses important cranial nerves that supply the whole of the head and the neck, from the back of the head to top of the head to the side of the head around the eyes and ears, the sinus area, the teeth, the chin and the throat.
During TMD, the muscles reposition the mandible (that may have been caused due to faulty occlusion or developmental anomalies like a large tongue, narrow arches, deep bite, high palate, compromised airways etc). Even erratic chewing habits like chewing on one side because of bad teeth on the other side can cause malposition of the mandible. The malpositioning would normally be an upward, backward and a lateral shift of the mandible. This would create a compression of the disc in the joint space. Any further jaw movements like talking, chewing and laughing would cause wear and tear of the disc. The two bones does meet and hence you hear the click during the jaw movement. This click is the initial symptom which is seldom cared by the patient. Further, any jaw movements would cause wear and tear of the bone that would end up as the bones fusing together, restricting the Mouth Opening further and further till the patient ends up with a jaw lock. Frequent jaw locks end up as an ankylosed joint.
Due to the loss of joint space, the nerves in and around the TMJ complex gets compressed leading to NMD pain symptoms.
Centric Occlusion(CO) and Centric Relation(CR) are terms that have always ended up pushing the mandible upward and backward. But for a TMD patient, isn’t it that very same CO that has led to the problem? What all we do, to try and coerce that patient into CO….the Dawson’s technique, the forced swallow technique, the hand in mouth technique! Have you ever given it a thought that while forcing the patient to bite into that CO, you may be actually pushing the mandible and hence the condyles, backward and upward into the retrodiscal pad of the glenoid fossa? That CO may only be his habitual occlusion, which his body may have self-repaired to compensate for that small occlusal discrepancy, which we always tend to overlook. The muscles of mastication that act upon the mandible have been trained by our CNS to keep the condyles there and hence the mandible in that erroneous position to avoid that high point! Any interference in the mandibular path of closure will send a noxious signal to the brain resulting in an Avoidance conditioning Response, that will basically tell the mandibular muscles to avoid that path and take another. Continuous noxious signals create a sensory engram leading to the muscles controlling the mandible to become hypertrophic in the new path. Hypertrophic muscles are shorter in length. Since, the articular disc in the TMJ complex is, virtually the continuation of the superior head of the lateral pterygoid muscle, any shortening of the muscle will result in the anterior displacement of the disc. The recapture is heard as the click which we can diagnose as Internal Disc Derangement (IDD) with Reduction. Further shortening, like in chronic patients, end up as IDD without reduction.
The airway is an elastic pipe structure that has inlets from both the nose and the mouth and proceeds to the lungs. The airway is virtually formed by tissues which are majorly the muscles which are in the craniofacial complex. Any compression in the muscle functioning would lead to a pathological compensatory malfunction of the airway.Authored By : Dr. Rajesh Raveendranathan