• The korean journal of orthodontics
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• v.23 no.4 s.43
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• pp.645-660
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• 1993

In this study, effects of incision of retrodiscal tissue and unilateral occlusal reduction on temporomandibular joint of rabbit were investigated. Twenty-seven adult New Zealand White Rabbits, weighing over 3.5kg, were utilized in this study. Temporomandibular joint surgery was performed in left temporomandibular joint of 24 rabbits to displace disc anteriorly through incising the retrodiscal tissue 1-2mm posterior to the disc. They were divided into two groups : twelve were left untreated after surgery, occlusal reduction was performed on left posterior teeth every 2 weeks in the other twelve rabbits, The remaining three served as the control group. The sample were sacrificed by 8, 12, and 16 weeks after surgery. Histologic examinations were performed after sacrificing them. The results were as follows : 1. Histologic findings which were manifested by flat articular fossa, broad articular surface, generalized recession of articular cartilage and sclerosis of subchondral bone were observed. These findings were similar to internal derangement. 2. In the rabbits untreated after surgery, thin cartilagenous layer and necrotic tissue were observed in 8 weeks group, calcifying cartilagenous layer was observed in 12 weeks group, and cartilagenous layer on anterior portion was observed in 16 weeks group. So, it showed gradual healing pattern into the normal tissue except displaced disc. 3. Occlusal trauma after surgery resulted in generalized recession of upper and lower articular surface. Necrosis and vertical split on condylar process of mandible were observed in 8 weeks group. Osteoclasts, exposure of subchondral bone due to erosion on upper and lower articular surface, and degenerative changes on retrodiscal tissue were observed in 16 weeks group. So, it showed continuous prowess pattern of osteoarthrosis.

• The korean journal of orthodontics
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• v.23 no.4 s.43
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• pp.455-474
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• 1993

Degenerative joint disease(DJD) has hun 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 axe 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, PH-ArGo, SArGo and Y-sxis angle increased significantly, but genial angle showed no significant difference. The means of hか 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 faical height(AFH), upper anterior facial height(UAFH) and lower anterior facial height (LAEH) of DJD showed no significant increase as compared with those of the noraml 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 of the condylar head and neck.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.13 no.1
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• pp.44-52
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• 1991

Internal measurement technique has been commonly and classically used to guide down-fractured maxilla by Le Fort I osteotomy into its new position during intraoperative procedure for correlating preoperative model works with surgery. However, It has been challenged now by several authors due to some problems as its inaccuracy in three-dimensional changes at surgery, difficulty to measure during surgery and impossibility of rechecking at the end of surgery etc. The purpose of this study was to evaluate the accuracy of maxillary movement by external measuring technique and to determine its accuracy between the prediction tracing and a new maxillary position. The results indicate that the external measuring technique was predictable in the vertical, horizontal and transverse change of the maxilla as its prediction, however, it has a tendency to shift the maxilla more anterior and inferior in overall direction than prediction. Post-operative canting difference were mimic, however Ehange of the maxillary dental midline was large and had a right-shifting tendency.1 The precise methods to keep maxillary dental midline as same as prediction and the avoidance of uneven force applied to the mandible for autorotation should be necessary during surgery in use of external measurement technique.