TMJ:What is Disc displacement?

What is discus displacement?

Discus displacement in the jawDiscus displacement in the jaw

Discus displacement is an expression for the deviation of the discus position from an arbitrarily fixed “standard” position.

The discus is a kind of cartilaginous spacer between the mandibular condyles and the sockets. Discus displacements are often differentiated between discus displacement with reposition and discus displacement without reposition.

The diagnosis of “displaced discus” arises from a very mechanical view of the human body. Till today it has not been established whether a clear physiological position for the discus exists at all. Many people have a displaced discus but no problems whatsoever. Then again, there are others who have no displacement but nevertheless have problems with the joint of their jaws. Many doctors are moving away from rigid concepts because of new discoveries. The discus position seems to be losing significance in respect to jaw joint complaints.

According to the old concept a definition of displaced discus with reposition exists when the discus, in the course of movement of the lower jaw, “jumps” back onto the mandibular condyle. A displaced discus without reposition, according to the old concept definition, exists when the discus doesn’t jump back on the mandibular condyle but rather remains displaced during the entire movement of the lower jaw.

The symptoms if a discus displacement (DD) are very variable. Jaw-cracking, for example is not a sure symptom of discus displacement. A DD is not always associated with pain either. Hypotheses about the origins of DDs have have changed very much in the last 70 years, starting from a mechanical model, moving more and more into physiological theories and now we’re moving into bio-psycho-social concepts.Biopsychosocial in the listing of DD as an illness means that genetic, social and pyschological factors play a part. The causes of the formation of DD with or without reposition are not easily explained. What is interesting is that women suffer from illnesses of the jaw joint far more frequently than men do.

The diagnosis of a DD with or without reposition is nowadays formed on the basis of clinically occurring symptoms. As a rule, treatment initiatives on the basis of unresolved existence of DDs depend on the symptom. In other words you yourself ultimately decide whether a DD is to be treated or not. If you don’t have any, or have hardly any problems then there’s no indication for treatment.

A discus displacement without reposition is not usually fully treatable since a manual reposition of the discus normally only very rarely works. Non-surgical treatment measures (such as splints) are usually aimed at reducing the adverse effects of DD. Occlusion splints can indeed, depending on the severity of the problem succeed in obtaining a reposition of the discus. The result however cannot be securely stabilised. A reduction in the problem will, independently of the discus reposition, also be achieved after a short period of wearing the splints.

Otherwise there are surgical measures available which may be aimed at discus reposition, discus removal (discectomy) or pain relief througn rinsing of the jaw joint (arthrocentesis with lavage). None of these methods however have been able to demonstrate any advantage when compared to non-surgical treatments.

The following is a summary of symptoms and treatment of DD:

  • Jaw joint cracking is not characteristic of a DD with reposition
  • A DD without reposition is often correlated with a sudden temporary reduction of the opening of the jaw
  • DDs are not always associated with pain. Pain is however more common with DD without reposition
  • The risk of a DD with reposition becoming a DD without reposition cannot be established scientifically
  • The chance of reposition of the discus gets less with the progress of time with a DD
  • DD pain is very treatable. The altered discus position is not
  • It is not necessary to treat a DD which doesn’t cause problems
  • As a result of a DD without reposition degenerative changes of all the joint structures may occur. Clear changes to the structures can be established morphologically. Nonetheless these are considered to be self-limiting adaptation occurences
  • With the application of conservative treatment measures the pain symptoms and the width of the opening of the jaw can be positively influenced in patients with DD without reposition however they can rarely be completely overcome
  • Pain symptoms influence one’s quality of life more strongly than the limited opening of the jaw
  • Why some patients experience a change and remain virtually pain free whilst others remain prone to serious problems is still not clear
  • There have been and are very many useless treatments on offer for DD, such as, for example Pulsing Signal Therapy (PST) or athrocenteses
  • The clinical results for existing DDs improve significantly during an observation period of close to 2 years
  • Since the necessity for treatment is determined by the clinical symptoms as opposed to the findings of investigations conservative methods of treatment should be preferred

 

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