Temporomandibular joint disorder (TMD) is any disorder that affects the temporomandibular joint (TMJ). The TMJ is the articulation between the lower jaw (mandible) and the temporal bone of the cranium. It is one of two only joints in the body having the function of two types of synovial joint - hinge and sliding. Movement of the joint occurs in three dimensions and is a complex interaction of the elements of the joint and nueromuscular control of several muscles attached to the mandible and the joint. As the jaw opens the mandible rotates around an axis through the medial poles of the condyles until the disc between the (condyles of the) mandible and the (articular eminence of the) cranium reaches the end of travel permitted by the ligaments attaching it to the condyle. This occurs when the jaw has opened by about 20mm. Further opening of the jaw requires the condyles to slide (translate) down the eminence until full opening is reached. Normal opening of the jaw with healthy TMJs is in the range of 40 - 60mm.
The most common symptom of TMD is pain in the jaw which may be accompanied by restricted movements of the jaw. There are many causes of pain that present as jaw pain and careful diagnosis is essential to differentiate between pain eminating from the TMJ and elsewhere. Apart from intra-capsular disorder of the joint, TMDs may also arise from masticatory muscle disorders or pain referred from elsewhere (such as cervical pain emanating from the neck). It is also the case that a patient may present with more than one of these conditions as one disorder can lead to another. Other symptoms of TMD include: - locking of the jaw - a load click, pop or grating sound when the jaw opens or closes - slow opening/closing of the jaw - deflection/deviation of the jaw when opening/closing - difficulty when chewing - tired or sore facial muscles
Our approach to investgating TMD begins with a detailed history in order to obtain a sound understanding of the patient's primary complaints and concerns, factors that may affect the condition and how it has manifested itself over a period of time.This is followed by clinical examination that includes observation of any signs of occlusal disease, palpation of the masticatory muscles, load testing of the TMJs, checking for occlusal interferences and an x-ray investigation. It is not uncommon for a person to experience one or more of the TMD symptoms for a period of time and for these to clear up without any treatment. The TMJ has a good capacity to adapt and to recover without intervention. Accordingly conservative treatment based on proper diagnosis is preferred before proceeding to irreversible procedures such as equilibration, orthodontics or surgery. It is possible to classify every type of TMJ disorder and to verify each classification by examination. Furthermore, improved understanding of the adaptive capacity of the components of the TMJ has improved our ability to identify problems not only within the joint but also in the connected tissues.
Biometric instruments are a very useful tool in clinical investigation of TMD as they can accurately measure key parameters of the TMJ in a manner that is both objective and repeatable.
The Piper classification of intra-capsular TMDs decribes the structural disorders that can be related to the symptoms routinely observed clinically. This classification specifies several stages of progressive deterioration as the TMJ progresses from full health to degenerative disease. In practice the degeneration may not occur sequentially but may involve passing back and forth between different stages. Furthermore, because of the joints ability to adapt the patient may experience painful episodes followed by painfree periods though the condition of the joint continues to deteriorate. It is therefore important to investigate TMD
The treatment regime will depend on the source of pain. For inflammation of the joint a diet of soft fruit and avoidance of the behaviours that may have caused the problem may be appropriate. This can be supplimented by non-steroidal anti-inflammatory drugs and hot/cold packs to relieve the pain and speed up recovery. Where premature tooth contact is confirmed by computerised bite analysis then equilibration (reduction) of the offending tooth may be appropriate. Where intracapsular disorders have been diagnosed the treatment plan will depend on the stage of degeneration of the joint. During the earlier stages muscle relaxation and counselling are often prescribed. In later stages recapturing the disc (which has slipped forward) may be done in conjunction with equilibration or supplimented by splint therapy.