In order to observe TMJ in a motion study, a protocol of 6 images was developed. MR images of the TMJ in multiple phases of opening were obtained by using the “fast scanning” capabilities of the GE RESONA MR system.
A short flip angle (gradient recalled acquisition in the steady state, or GRASS) “fast scanning” technique was used to assess functional TMJ dynamics.
GRASS is routinely used to image the joint from closed to maximally open position and back to closed again. While using the technique, areas of high intensity spot were noticed in the anterior of the upper and lower joint compartment. Blood vessels, synovia, effusion and fat artifacts were suspected as possible causes of the high intensity spot.
The flow compensation technique and method of changing the slice thickness in GRASS were used to examine these possible causes. We found that the intensity spot in the anterior joint compartment was probably a partial volume effect caused by synovia and effusion rather than blood vessels or fat artifact.

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Video-fluorography was performed on 156 temporomandibular joints just before arthrography. Condylar movements during jaw opening, closing and protruding were recorded on video cassette. The parthway and position of the mandibular condyle were analyzed in each frame and 6 characteristic patterns of the opening pathway were found. The patterns of movements and the arthrographic findings were compared. In 16 out of 22 joints (73%) with anterior disk displacement with reduction, the opening pathway of the condyle showes “B” type movementthe velocity decreased at the midpoint of condylar translation. In “C” type movement-the condylar translated with minimun rotation at the early of opening, and rotation occurred at the late stage of the opening, 26 out of 29 (90%) showed soft tissue perforation. Video-fluorography might be a significant methods for the prediction of temporomandibular soft tissue conditions.

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Displacement of the articular disk was estimated from the characteristics of the paths of incisal points and kinematic points in both sides of the condyle. The clinical measuring system allowed easy measurement of the three dimensional mandibular movements. The system used two sets of Selspot cameras and light landmark sets, each with three LEDs attached on the upper and lower incisors. The accuracy of the measurement was 0.6mm (0.4 %).
Thirteen subjects with internal derangement of the temporomandibular joint and eleven subjects in normal condition were examined. In the case of anterior disk displacement with reduction, the reduction and redisplacement of the disk were diagnosed by analyzing the paths of kinematic points in the sagittal plane. In the acute cases which were already diagnosed as no-reduction, the progress of disk displacement was estimated quantitavely by comparing the paths of both side kinematic points. The same estimation was achieved by analyzing the path of the incisor in the sagittal and coronal plane.

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Orthodontic treatments were applied in five cases of TMJ internal derangement. Two cases of TMJ internal derangement with clicking, treated by orthodontic treatment are presented. Case 1 was a 14-year-old male who had a clicking sound in left TMJ, and who primarily received repositioning splint therapy. However prosthetic reconstruction of the occlusion was difficult because of severe crowding of the teeth. Case 2 was a 15-year-old female with rotation of the upper central incisors which seemed to induce disturbance of the TMJ anterior movement. Thus orthodontic treatments by the multibracket system were performed. After the treatment, the patientshad no TMJ symptoms, and any recurrence has not been noted at either the 10-month and 20-month follow -up. Selective orthodontic management of malocclusion in partients with internal derangement is therefore recommended as an appropriate treatment in non-surgical therapy for TMJ derangements.

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A sample of 3108 students from eight high schools in Japan was investigated by means of a two-item questionnaire. The questionnaire included the occurrence of symptoms or signs of mandibular arthrosis and the history of external force on the mandible in junior high.
Statistical analysis of the data showed that the symptom-rate of students with a history of external force on the mandible was higher than those with no history.
It is suggested that the prevalence of mandibular arthrosis in young people might be associated with the history of external force on the mandible in their younger days.

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For the diagnosis of TMJ internal derangement, it is important both to clarify the shapes and the relation of condyle and articular disk, and also to undertake functional analysis of TMJ movement.
Recently the effectiveness of TMJ fluoroscopy has been recognized.
However, it is sometimes difficult to interpretate its because the surrounding bones overlap the TMJ components.
In the present study we tried to apply a digital subtraction system, which is already widely used in clinical medicine for TMJ fluoroscopy and compared its image with the traditional fluoroscopic one. The digital subtraction system can remove the overlapping of surrounding bones and make it easy to observe TMJ components. By using this system in MASK mode we observed a flow of contrast medium indicating the shape, location and existence of perforation of articular disk more clearly than the traditional method.
Using Time Interval Difference (TID) mode we observed TMJ movement (from opening to closing of mouth) more accurately than before. This mode is effective for the classification and analysis of TMJ internal derangement which shows various disturbances of movement. Furthemore, it might be possible to compare the data by this method with those obtained by using other TMJ movement, analysis equipment.

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In order to clarify the occurrence and location of intracapsular conditions, arthroscopic examination was performed on 54 joints of 39 patients with clinically diagnosed closed lock of the temporomandibular joint.
The results were as follows: synovitis was noted in 51 joints (94%). it was often observed not only on the posterior pouch (93%) but also on the anterior recess (73%) and in the medial capsule (70%). Adhesions existed in 42 joints (78%), predilected on the anterior recess (62%) compared to other sites (about 30%). They often formed wall-like and/or pleat-like areas on the anterior recess and lateral capsule, and formed pleat-like and/or band-like areas on the posteroir pouch and medial capsule. In about half of the joints with synovitis, the synovium was covered with a white thin membranous substance, which seemed to be associated with the formation of adhesive lesions. The articular eminence lacked in marked pathologic findings at the early stage of arthroscopy. However, in more than 80% of the joints, the surface of the eminence showed fibrillation of the fibrocartilage or exposure of the underlying bone during the arthroscopic examination. Perforation and or deformity of the disk was often observed, but fibrillation was not noted. Capillary was often observed on the articular eminence and fossa. In two patients without disk displacement, translation of the disk was limited by adhesive lesions in the joint.

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The authors developed and applied clinically a new technique (middle-lateral approach) of inferior joint compartment arthroscopy of the temporomandibular joint, based upon the results of the anatomical study which was reported earlier. The needle arthroscope devised for the inferior compartment was employed, with a diameter of 1.2mm, and a length of 32mm. Five adult fresh cadavers (5 joints) were prepared for the anatomical study and 11 patients (16 joints) received diagnostic arthroscopy of the inferior compartment. The middle-lateral approach was as follows; 1) insertion of an 18 gauge needle from the skin point 7mm inferior to the condylar head, 2) placement of the needle tip to contact the condylar neck perpendicularly, puncturing the inferior compartment along the lateral bone surface from the inferior direction, 3) exchanging the needle for a mandlin by insertion through the needle, 4) insertion of the arthroscopic cannula as a guide of the mandlin, 5) arthroscopic examination of the compartment under distension by saline. Using this technique, all 5 cadavers were punctured successfully without any iatrogenic disk perforation. In the clinical application, all joints were treated with this technique excepted for 2. Both the anterior and posterior recess were successfully examined. However, the medial part of the compartment was limited in arthroscopic detection.
The middle-lateral approach is therefore recommended as a reliable and safe technique for inferior compartment arthroscopy of the temporomandibular joint.

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In the habitual dislocation of the temporomandibular joint, though the etiology is not clear, many cases seem to be controlled by selflimitation of their jaw movements.
Scarification of the oral mucosa and temporal tendon, which is one of the treatments in these cases, has many advantages. These include its easy of application, intraoral approach, and the lack of major complications.
We examined 6 such cases in the period from 1985 to 1991 at our hospital. These cases were 3 males (20-80 year-old) and 3 females (19-30 year-old), and they had a history of habitual dislocation for 2 to 10 years.
Under local anesthesia, all of the 6 patients were operated on using the method of vertical dissection of the oral mucosa and horizontal closing of the temporal tendon, reported by Maw et al. and Gould.
These cases were followed for at least a year to confirm the effectiveness of this procedure in preventing mandibular dislocation and in reducing the maximal mouth opening, and to observe possible surgical complications.
As a result, the prognosis of all cases is comparatively satisfactory, and there were no complications and no recurrence within 1 year after surgery.

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It is likely that the contralateral side of the temporomandibular joint is affected in patients suffering from unilateral temporomandibular joint dysfunction, because both joints are connected to the rigid mandible. The purpose of this study was to ascertain the prevalence of anterior disk displacement on the contralateral side in consecutive 112 patients with unilateral temporomandibular dysfunction. 47% of the total patients had anterior disk displacement on the contralateral side, whereas 73% had it on the symptomatic side. Prevalence of anterior disk displacement on the contralateral side increased in proportion to the degree of anterior disk displacement on the symptomatic side.

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A 74-year old man visited our department, complaining of difficulty in closing his mouth, and his condition was complicated by a destroyed lung.
The bilateral temporomandibular joints was made without success. Open reduction according to the Myrhaug's eminectomy was performed under local anesthesia.
There has been no recurrence of dislocation since the operation.
Myrhaug's eminectomy seems most effective for prevention of recurrent dislocation of the temporomandibular joint. Several problems in the mode of treatment are discussed.

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This study reports a case of temporomandibular arthrosis thought to be induced by peculiar dual bite forcing the condyle to displace forward. This resulted flom many years' continuous use of a high template incurring an openbite of the molar region. The openbite in turn induced a back-down rotation of the mandible and a backward displacement of the condyle on the right with an abnormal contact of 2:32. Thes features were noted on the removal of the appatatus.
In treatment of this case, the aim from the start was to improve the two peculiar types of occlusion at the same time. Particular attention was given to adjustment of the vertical dimension of the occlusion, In order to create the proper habit of occlusion. The purpose of this was to readjust the muscular function affected by malocclusion over a long period of time.
The progress of treatment for this case was followed using occlusal sound waveform to gather diagnostic data occlusal amelioration. It was confirmed that the varied abnormal waveform was corrected. Furthermore in parallel with this, such symptoms as temporomandibular pain, trismus and clicking strikingly improved as the occlusion improved.
The study indicates that a close correlation exists between the restoration of the temporomandibular condyle, normalization of occlusion and the waveform of occlusal sound. Moreover, the usefulness of examination based on occlusal sound waveform was confirmed.

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