A quantitative measure of mandibular joint dysfunction: phase plane modelling of jaw movement in man.

Jaw movement during the open-close-clench cycle was recorded using a Hall-effect generator and a small permanent magnet affixed to opposing incisor teeth. Computer programs provided graphic display of jaw-closing velocity as a function of jaw position (the phase plane) and determined the error between the experimental data and a mathematical model. A large error indicated dysfunction and predicted successful treatment by accepted occlusal therapy; a small error indicated normal function or predicted unsuccessful occlusal treatment. These oblservations suggest that phase plane modelling provides a quantitative measure of joint dysyunction that may be used in monitoring treatment progress and in separating clinically diagnosed dysfunction into two categories-one which responds to occlusal therapy, andone which does not.