Relationship between the sound in temporomandibular joint and the morphological aspects in adolescent orthodontic patients with anterior open bite

Abstract

The purpose of this study was to investigate the relationship between sound in the temporomandibular joint (TMJ) and morphological aspects in adolescent orthodontic patients with anterior open bite. The selected subjects were 40 patients of the Orthodontic Clinic of Hokkaido University Dental Hospital who had anterior open bite and were less than 15 years old at the first examination. ClassIII patients were excluded from the study. The subjects were divided into two groups : one group of 17 patients who exhibited sound in TMJ before and/or during orthodontic treatment (symptomatic group) and one group of 23 patients who did not exhibit temporomandibular disorders (asymptomatic group) . Lateral cephalograms were used as materials. The following results were obtained : 1. The symptomatic group included 42.5% of the subjects. 2. In skeletal pattern, patients in the symptomatic group had a significantly more-posteriorly inclined ramus and narrower gonial angle than did patients in the asymptomatic group. Patients in the symptomatic group tended to exhibit more skeletal Class n jaw relationships and a shorter ramus than did patients in the asymptomatic group. 3. In denture pattern, there were no differences between anterior tooth inclinations in the two groups. These results suggested that many adolescent orthodontic patients with anterior open bite have sound in the TMJ as well as a posteriorly inclined and short ramus.