Abstract
Mandibular border movements were recorded at the incisal point for 168 patients with internal derangements of the TMJ, which were ascertained by MR images. On the basis of MRI findings including bilateral TMJs, the status of the discs were classified as reducing, nonreducing and sideways disc displacement. The characteristics of border movements and frequencies of restricted movement in various types of disc displacement were investigated. In addition, a follow-up study was undertaken to examine the transfer frequencies from reducing to nonreducing conditions of the disc.
The results were as follows.
1) There was no difference in mandibular movement between unilateral and bilateral cases in patients with internal derangement of the TMJ.
2) In unilateral cases, reducing cases indicated only unilateral restriction of the mandibular movements, while nonreducing ones chiefly bilateral restriction. These tendencies were also true when reducing and nonreducing groups included bilateral cases.
3) Restriction pattern of mandibular movements in patients with sideways disc displacement was rather similar to that of nonreducing cases as compared with reducing cases.
4) Affected side of movement restriction, instability of maximum opening position, and W-shaped limitation of opening range enhanced to evaluation of TMD conditions, especially disc displacement.
5) Six percent of 62 patients in the reducing group, including sideways disc displacement were transfered to the nonreducing, roup during the follow-up period.
