Range of motion
This is the only truly measurable parameter, as the others are more subjective. It is just as important to record jaw movement as a means to assess the rate and degree of improvement as it is to determine the severity of symptoms.
Movements to be measured are:
Incisal opening - pain free limitIncisal opening - maximum (forced)Lateral mandibular excursionsMandible deviations on pathway of openingIncisal opening
The incisal opening is measured from the upper incisal tip to the lower, with the patient first of all opening to the limit of their comfortable, pain free range. This is then compared to the normal range of motion (see right). Their maximum (forced) limit is also recorded. It is important to determine whether a limitation of vertical movement is due to pain or a physical obstruction. If it is pain, then it may be a muscular problem, if an obstruction, then disc displacement is most likely.
Lateral Excursions
The lateral movement should be measured from mid-line to mid-line, the patient moving the mandible to their maximum extent, from one side to the other.
Mandibular deviation
When the jaw is opened, the path it follows should of course be straight and consistent. Deviations from the norm are either lasting ortransient, and are all suggestive of internal derangements of different sorts.