The purpose of this study was to elucidate odontogenic risk factors for juvenile onset temporomandibular disorders. 54 patients were diagnosed with this disease at Nagoya University (Dent-Oral Surgery, School of Medicine) and Fjita Health University (Dent-Oral Surgery, School of Medicine). A case control study was performed based on these cases to evaluate occlusion, tooth materials and dental arch structure. The results are summarized as follows.
1. The percentage of subjects with Hellman's occlusal developmental stage IVA was 87% in the patient group; this stage was the most numerous.
2. Angle's classification II and III were seen in 42.6% and 29.6% of the patients, respectivery these percentage were significantly higher than those in the control. The relative risk of temporomandibular disorders with Angle's classifications II and III was 12.26 and 38.40 respetively.
3. The percentage of subjects in the patient group with malocclusion was significantly higher than that in the control group. The most frequent types of malocclusion in the patient group were crowding (53.7%) and upper protrusion (29.6%); The relative risk of temporomandibular disorders with these conditions was 6.96 and 6.40, respectively.
4. Of the subjects in the patient group, 25.9% had 31 teeth. The relative risk of temporomandibular disorders with this anomaly was 3.36.
5. In 31.5% of the patients the teeth were asymmetrical both verticaly and horizontaly. The relative risk of temporomadibular disorders with this condition was 2.41.
6. The average maxillary basal arch length in the patient group was 19.8mm, while the average mandibular basal arch length was 18.4mm. In normal controls, the average maxillary basal arch length was 23.3mm, and average mandibular basal arch length was 20.3mm. Therefor, significantly smaller values were obtained in the patient group.
7. A significant majority of the patients showed a centrifugal inclination of the second upper molar.

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The risk of damage to the facial nerve by several arthroscopic punctures to the superior joint compartment was studied on 34 joints in 17 adult fresh cadavers.
The punctures were undertaken by infero-lateral, antero-lateral, and endaural approaches. The results showed no macroscopic injury to the nerve bundles. The averaged closest distance from a trocar sleeve to the facial nerve was 6.7mm in infero-lateral, 2.5mm in antero-lateral, and 10.9mm in endaural approach, respectively.
In addition to our clinical experiences, the arthroscopic punctures may not be the main etioligy of facial nerve weakness. The TMJ surgeon, however, should keep in mind to eliminate of a violent maneuver for prevention of facial nerve complications.

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In mass screening for temporomandibular dysfunction, epidemiological survey on function and disturbance of T. M Joint has been made in 3348 adult persons (2757 males and 591 females, mean age 35.2 years old). We classfied the TMJ dysfunction according to (A) maximal mouth opening, (B) TMJ sound, (C) muscle pain, (D) TMJ pain on palpation, (E) TMJ pain on movement of mandible and (F) daily life disturbance by TMJ dysfunction. One score point was given to the five clinical symptoms (A-E) when they are positive findings. TMJ dysfunction score was added as dysfunction score ranging from 0 to 5 points for each individual. Percentage distribution of material according to dysfunction score (DS) was as followings. DS-0: 79.5%, DS-1: 18.4%, DS-2: 1.7%, DS-3: 0.3%, DS-4: 0.1%, DS-5: 0.0%. 686 persons (20.5%) had been found some clinical symptoms. The most frequent symptopm was TMJ sound (15.3%) whereas symptoms related to the pain were low percentages (3.8%). Daily life disturbance by TMJ dysfunction was correlated with TMJ dysfunction score. Young women group, whose average dysfunction score was 0.16, complained daily life disturbance by TMJ dysfunction more than 60 years old women group that had the highest average dysfunction score (0.47).

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Although there have been many researches on the cause of primary symptoms, immanent factor and psychological factor of TMJ arthrosis in young people, the method of the treatment for those diseases have not been established. After we treated finally those patients, We investigated the change of symptoms in young people arthrosis by questionnaires.
72 patients of young people arthrosis were selected for this study who had underwent primary treatments and responded to the questionnaires at the Tokyo medical and Dental Univ. Department of oral and maxillofacial surgery from 1983 to 1987. There were 20 males and 52 females. It was the group of efficacy that after primary treatment, 3 main symptoms (clicking sound, limited movement and pain) were gone. On the otherhand it was invalid group that 3 main symptoms remained. In 50 patients that were investigated the condition of tooth crown surface at the primary treatment, we examined the change of the symptoms by questionnarires. The results as follows:
1. According to the results of the questionnaries, primary symptoms were vanished in 17 cases of 47 invalid cases.
2. In 15 cases of 25 effective cases, primary symptoms recurred at the time of the questionnaries.
3. The patients with limited movement of mouth at the primary diagnosis, were mainly cured at the time of the questionnaries.
4. There were no difference of the symptom recurrence at the time of the questionnaries between the patients who were treated for occlusal adjustments and were not.
5. There were many recurrences at the time of the questionnaries in the effective and invalid group that were already treated for dental surface at the primary diagnosis.

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The purpose of this study was made to evaluate the influence of afferent sense from the teeth surrounding structures and the temporomandibular joints (TMJ) on the silent period (SP) of the anterior temporal and masseter muscles. The SP during tooth tapping and chin tap were recorded in five men subjects. The authors selected normal subjects who investigated the following conditions: (1) Normal conditions (stage I), (2) Local anesthesia of mandibular teeth (stage II), (3) Local anesthesia of mandibular and maxilla teeth (stage III), (4) Local anesthesia of TMJ (stage IV), (5) Local anesthesia of TMJ and all teeth (stage V). The following results were obtained:
1. The prevalence of SP during tooth tapping and chin tap showed significant differences in the relations between stage I and stage II, stage V.
2. The prevalence of SP during chin tap was more than SP during tooth tapping.
3. The SP latency (L) and duration (D) of stage I during tooth tapping showed significantly shorter SPL and SPD of stage V. But a variance of SPL was bigger than SPD.
4. The SPL and SPD of stage I during chin tap showed significantly longer than SPL and SPD of stage V. But a variance of SPL was bigger than SPD.

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The purpose of this study is to evaluate the utility of right-left asymmetry in temporal and masseter muscles activities on subjects as the parameter for diagnosis of stomatognathic dysfunction. Both clenching and tapping movement were adopted as tasks on each subject with and without stabilized occlusion bilaterally. Consequently, in voluntary clenching, the intention side on which each subject made effort to exert bite force, influenced the right-left asymmetry in muscle activities considerably. In addition, the right-left asymmetry in temporal muscle activities during tapping was suggested to be caused by the unbalance of occlusal contacts.

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Synovial osteochondromatosis is a benign lesion of synovial membrane origin. It occurs most often in the metaphyseal regions of long bones, and is relatively uncommon in the temporomandibular joint. We report a case of Synovial osteochondromatosis of the temporomandibular joint with hypertrophy of the condyle. The patient was a 66-year-old man, complaining of dull pain in the right temporomandibular joint. Radiographic examination, CT scanning, and the double contrast arthrographic findings showed that the right condyle was enlarged with irregular radiopaque masses lying above the external of the condyle. Also, there was a perforation of the disk, and the joint space had narrowed. Bone scintigraphic findings showed a hot spot at the right mandibular head. We operated on this patient with a clinical diagnosis of tumor of the mandibular head, but histopathological examination showed Synovial osteochondromatosis. There were no significant complications at 1 year and 7 months after the operation.

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Two cases of TMJ fibrous ankylosis caused by trauma were reported. The first case, 45 year-old-woman, was refered for severe bilateral TMJ pain with difficulty in opening the mouth (26mm) over 3 years after facial trauma. Arthrography revealed fibrous adhesion and deformed disks in the capsules of both TMJs. Osteophyte was found on the condyle of the left side. After resection of fibrous tissue, disks, and osteophyte, intensive physical therapy was appied postoperatively for increase in mouth opening range. 4 years after the operation she was able to open her mouth 35mm and eat hard food without disturbance.
The second case, 41 year-old-woman, visited our clinic because of gradually decreasing range of the mandibular movement. At the initial visit the maximal opening mouth range was 24mm with severe TMJ pain on the right side. After diagnosis of the fibrous ankylosis by arthrography, fibrous adhesion and the deformed disk were removed with osteophyte on the condyle. Postoperative physical therapy was carried out. The patient could open the mouth 35mm one year after surgery.
In conclusion, arthrography was very useful for diagnosis of fibrous adhesion in the capule of the TMJ. Not only resection of the fibrous adhsion with the deformed disk but postoperative physical therapy played a very important role in increase in TMJ movement.

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15 patients with internal derangement of the temporomandibular joint had undergone the disc repositioning surgery. In an average follow-up period of 19 month, 8 patients were evaluated as “excellent”, 5 patients “good”, 1 patient “fair”, and 1 patient “poor”. The overall surgical success cases were 13 (86.7%). There was no surgical complication.

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Dual-space, double-contrast arthrotomography and arthroscopic lysis and lavage operation were sequentially applied to 35 temporomandibular joints (TMJs). Authors compared to double-contrast arthrotomographic findings with arthroscopic findings in superior joint compartment of the TMJ.
In 18 (51%) out of the 35 joints, adhesion in superior joint compartment was seen by both double-contrast arthrotomographs and arthroscopic examinations. Both arthrotomographic diagnosis and arthroscopic diagnosis were coincided in 30 joints.
In 10 joints, fibrillations in superior joint compartment were seen by arthroscopic examinations. In four out of the 10 joints, fibrillations were detected by double-contrast arthrotomographs. Thus, only four of 10 fibrillations were diagnosed arthrotomographically, those were illustrated by the low sensitivity.
Perforation was arthroscopically seen in four joints. Double-contrast arthrotomograph confirmed perforation in three out of these four joints and revealed perforations in twelve additional joints. Thus, only three of 15 perforations were diagnosed arthroscopically, those were illustrated by the low sensitivity.
Double-contrast arthrotomography was superior to arthroscopic examination in detecting disk displacement, disk configuration and perforation of posterior attachment of the disk. Arthroscopic examination was inferior to arthroscopic examination in fibrillation in superior joint compartment. In the information on adhesion in superior joint compartment, diagnostic accuracy was equal in both methods. Double-contrast arthrotomography had high diagnostic performance in pre-operative joints of arthroscopic lysis and lavage.

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Four hundred and eighty eight patients with TMJ arthrosis who visited our clinic between 1987 and 1990 were reviewed with respect to the symptoms excluding TMJ symptoms such as limited mouth opening, clicking or crepitus of the TMJ and pain in the TMJ and masticatory muscles (hereinafter called “Other Symptoms”) in order to study the relationship between TMJ arthrosis and Other Symptoms. Other Symptoms were observed in 324 patients (66.4%). The most frequent symptom was stiffness or pain in the shoulder, and/or neck, followed by migraine, otalgia, pain in the eye, tinnitus and stuffy sensation in the ear. Other Symptoms were observed more frequently in female than in male patients. The frequency is higher in the patients with the masticatory muscles pain, and lower in the patients less than 20 years old. More than 90% of the patients had Other Symptoms in the same side of TMJ symptoms.
Furthermore, in 90.5% of 105 cases whose clinical course of TMJ symptoms and Other Symptoms both could be followed up, the improvement of Other Symptoms was parallel with that of TMJ symptoms.
It seems that Other Symptoms seemed to be referred symptoms with TMJ arthrosis, if the symptomatic side of Other Symptoms and that of TMJ arthrosis is ipsilateral, and the improvement of Other Symptoms is parallel with that of arthrosis in the treatment course.
The questionnaire to 100 patients with TMJ arthrosis concerning Other Symptoms showed higher frequency than the previous data. Therefore, there is a possibility that clinicians may overlook Other Symptoms when interviewing to their patients, and patients may not complain of their Other Symptoms. Consequently, clinicians should have careful interview about Other Symptoms, paying attention to reference with TMJ arthrosis, and follow up the clinical course of both Other Symptoms and TMJ symptoms considering the necessity of transfer to professional clinics for Other Symptoms.

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Fractures of the condyle are not uncommon amongvarious types of the mandibular fracture. But a longitudinal fracture of the condyle is rarely seen, which does'nt belong to any classifications of a condylar fracture which usually bases on the height of fracture (intra-or extra -capsular) and acompanying with or without displacement or dislocation. We recently experienced a case of longitudinal fracture of the condyle, which we report with some discussion.
The patient, a 19-year-old man, came to our clinic referred from a dentist. Two days previously he had fallen and his chin had been struck. He presented a tender swelling of the mental and left preauricular region, anterior open bite and trismus with 25mm interincisal distanse when opening mouth. Orthopantomogram showed a fracture of the mandible in the symphysis region but a fracture of the condyle, and neither sagittal tomograms of the temporomandibular joint revealed it. Finally, frontal tomograms of the joint and computed tomograms revealed a longitudinal fracture with displacement of a fragment involving inner pole.
The open reduction of the fracture in the symphysis region was performed under general anesthesia, simultaneously removing the small fragment of the condylar process which disturbed opening mouth, and totally resecting the meniscus severely deformed and displaced anteromedially, which was replaced with Silicon rubber sheet^®, Dow Corning Co. USA. The postoperative course was favorable, and the implant was removed three months postoperatively. Two years after treatment the function of the jaw was found to be excellent.

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