Cephalometric appraisal of the open-bite cases with the degenerative joint disease of the temporomandibular joint

Kim, Tae Woo

Abstract

Degenerative joint disease(DJD) has been known as one of the diseases which affect the middleor old-aged people. But as orthodontists are getting interested in the adult orthodontics, it is not rare for them to meet the open-bite patients with the TMJ DJD in their clinics. The purpose of this article is to investigate the cephalometric characteristics of the open-bite cases with TMJ DJD. Twelve TMJ DJD patients(15.1-39.5 years old) were selected from the patients who visited Department of Orthodontics. Seoul National University Hospital. Cephalograms were taken and means from 60 measurements were compared by t-test with those of the fifty four healthy adults(20.0-26.7 years old) who have normal occlusion and TMJ. In this study male and female are compared respectively, for in the normal samples 26 measurements showed significant differences between the male and the female. The results and conclusions ore as follows: 1. In DJD group, ANB and Angle of convexity decreased, which means the retruding of the mandible. The interincisal angle was smaller than that of the normal group. The means of the overbite were -2.1mm in male and -3.0mm in female, and the means of the overjet were 5.6mm in male and 6.7mm in female. The profile was similar to that of Angle's Class II div.1 open-bite. 2. SN-GoMe and FMA increased in DJD, but SN-PP and FH-PP did not show any significant difference. In TMJ DJD open-bite cases, the bony structure lower than the palatal plane seemed to play an important role in developing open-bite. 3. In DJD group, FH-ArGo, SArGo and Y-axis angle increased significantly, but gonial angle showed no significant difference. The means of ArGo were 50.1mm in male and 40.2mm in female, which were significantly smaller than those of the normal(56.5mm in male, 50.9mm in female). These findings seemed to indicate the posterior rotation of mandible resulted from the shortening of the ramus height. 4. Anterior facial height(AFH), upper anterior facial height(UAFH) and lower anterior facial height (LAFH) of DJD showed no significant increase as compared with those of the normal group. There was no significant difference in the ratio of upper anterior facial height to lower anterior facial height(UAFH/LAFH). But, lower posterior facial height(LPFH) was significantly smaller than that of the normal group. 5. It was thought that the peculiar profile of the TMJ DJD open-bite was resulted from the posterior rotation of mandible as the ramus became short following the degerative destruction of the condylar head and neck.