To evaluate the relationship between the onset evants and gender, age and type of TMD, 809 of 912 patients visited and diagrosed as TMD were investigated.
One hundred and ninety-eight patients (24.5% of 809 cases) noticed the onset events. The gender and age distributions were in significant. By type there were more patients belonging to type II and IV that noticed the onset events than those in type I and III, however no significant difference was observed between the other types respectively.
All onset events were classified into seventeen categories, and the most frequent 4 items were: wide opening of the mouth (62 patients, 31.3%), extrinsic trauma (40 patients, 20.2%), occlusal change (37 patients, 18.7%) and masticating tough food (35 patients, 17.7%). The percentage of these 4 items was 87.9%. As for extrinsic trauma, the rate of males was significantly higher than that of females. The age of the patients who noticed the occlusal change tended to be middle age.
The relationship of malocclusion, day clenching and night bruxism with the awareness of the onset event was statistically in significant.

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In asymtpomatic young-adult volunteers (22 males; 24 females; age from 20 to 28 years), position and configuration of the temporomandibular joint (TMJ) were examined using magnetic resonance (MR) imaging. Disk displacement was found in 54% of all volunteers; 71% in females and 36% in males. Bilateral disk displacement was more frequently found in females, while unilateral disk displacement was more prevalent in males. Disk configuration was biconcave in all volunteers without disk displacement, whereas disck in volunteers with bilateral disk displacement ware various in configuration.

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The direction of disc displacement and disc with or without reduction was observed to diagnose of temporomandibular joint disorder, and joint pain, trismus, deformed disc, bone change of the mandibular head and degree of mandibular head translation were compared them.
Six hundred eighty-two joints in 341 patients (72 males and 269 females) having temporomandibular joint disorder were examined. They were referred to our clinic, and the diagnosis was done by MRI from 1992 to 1997. The patients were examined with the mouth closed and maximally opened both in sagittal and coronal planes, and a 1.5 Tesla superconductive MR unit was used.
Disc displacement of 367 joints was anterior, 35 joints anteromedial, 9 joints medial and 271 joints negative. Disc displacement with reduction of 166 joints was anterior, 7 joints anteromedial and 4 joints medial. There was no relationship between the direction of disc displacement and joint pain, trismus, deformed disc and bone change of the mandibular head. The incidence of joint pain, trismus, deformed disc and bone change of the mandibular head in patients whose anterior disc displacement without reduction was higher than in those with anterior disc displacement with reduction. However, no statistical differences between anteromedial disc displacement with or without reduction and medial disc displacement with or without reduction were found regarding joint pain, trismus, defoomed disc and bone change of the mandibular head.
In conclusion, the lack of reduction of the disc, which was displaced anteriorly, would impair the degree of joint pain, trismus, deformed disc and change of the mandibular head.

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We have developed the prototype ultrasound computed tomography (US-CT) which enabled to reconstruct usual TMJ ultrasonographs to sagittal direction tomographic images. In this study, the prototype US-CT was evaluated using a human dry skull with freshly dissected pig atricular disc as a custum ultrasound phantom. The results showed that sagittal section images of osseous tissue around TMJ were clearly visualized. However, a joint cavity and an articular disc were seen only in lateral portion of the condyle head. These results suggest that the prototype US-CT can visualize a sagittal tomographic image of lateral part of TMJ.

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A case of secondary remodeling of the condyle by arthroscopic disc suture and fixation technique combined with intermaxillary traction.
This paper reports a case of rheumatoid temporomandibular arthritis where secondary remodeling of deformity of the condyle was achived by the arthroscopic disc suture and fixation technique.
The case was a 66-year-old male, who was referred, having been unable to masticate as a result of chronic rheumatoid arthritis. He showed mandibular retrusion and open bite. X-ray images showed deformity of the condyle and shortening of the mandibular ramus. Intermaxillary traction and arthroscopic disc suture and fixation technique was perfomed. After the therapy, the open bite disappeared and the patient regaind the ability to masticate and has retained good occlusion without mouth opening disturbance for 1 year and 2 months postoperatively. X-ray images postoperatively showed secondary remodeling of the condyle. These results confirm that this therapy makes possible secondary remodeling of the condyle.

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The purpose of this study was to investigate the clinical course of young patients who had been examined by magnetic resonance imaging (MRI), resulting in the diagnosis of anterior disk displacement without reduction of the temporomandibular joint (TMJ). The images examined in this study were sagittal images of the mouth in the opened and closed positions. The subjects were 30 patients (6 males and 24 females), aged 12 to 18 years (mean age of 15.4 years). Thirteen of the patients complained of arthralgia, 14 of trismus, and 3 experienced TMJ sound. Nonsurgical treatment with an occlusal splint was carried out for all patients, pharmacotherapy as an adjunct was utilized for 5 patients, and 1 patient who had rigid closed lock underwent arthrocentesis. The treatment duration for the 13 patients who had complained of TMJ pain averaged 8.8 months, and that of the 14 patients with trismus was 10.2 months; arthralgia (11/13 cases) and restricted mouth opening (12/14 cases) conditions had improved in most cases. Ten of the 30 patients had mouth opening width greater than 40mm in spite of the nonreducing anterior disk displacement detected by MRI.
A prognostic investigation by the telephone questionnaire was performed in 28 of the 30 cases. No patients complained of trismus after the primay treatment, 3 patients complained of intermittent arthralgia, and 9 patients had TMJ sound, but no patients made any further visits to clinics for treatment.

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