PHYSICAL-MECHANISMS INVOLVED IN THE GENESIS OF TEMPOROMANDIBULAR-JOINT SOUNDS

Several different mechanisms are potentially capable of generating sou nds in the temporomandibular joint (TMJ). These include impact, slidin g anal stick-slip friction, fluid dynamic effects and the release of e lastic strain energy. It is the aim of this paper to provide a framewo rk with which to separate sounds resulting from the different underlyi ng causes. Each mechanism is described and its relevance to TMJ sounds and clinical significance discussed. Since it is not possible to obse rve these mechanisms in vivo the arguments are based mainly on analogi es which are used to make predictions of the characteristic acoustic s ignatures of the sounds produced by these different mechanisms, In par ticular the changes in the characteristics of the sounds as parameters such as mandibular speed and loading are stressed. It is suggested th at single short duration sounds (clicks) are due to impact, multiple s hort duration sounds (creaks) to stick-slip friction and defects of fo rm and long duration sounds (crepitus) to simple sliding friction. Sev eral other mechanisms which have no obvious clinical significance but which are capable of producing similar sounds are also described and m ethods of distinguishing them from the sounds that do have clinical im plications are discussed.