It is said that recurrent dislocation of the temporomandibular joint (TMJ) is caused not by abnormal bone formation but by organic or functional changes of the soft tissue of the TMJ. Since there is no unified opinion about the etiology of this condition, many treatments are recommended. This paper reports a clinical study of 16 joints in 10 patients which were in need of surgical treatment. They were examined by radiography, double contrast arthrographic computed tomography (10 joints in 7 patients) and magnetic resonance imaging (6 joints in 4 patients). These showed that the hard tissue of the TMJ in these patients was almost normal radiographically. It is suggested that the crisis factors are abnormality of the neuro-muscular system caused by changes and collapse of occlusion or by central neuron system disease and drugs, anterior displacement of discs, abnormality of retrodiscal pads and relaxation of the articular capsule of the TMJ and lateral ligament. All cases were successfully treated by Dautrey procedure, so it seems that this procedure gives the best results.

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Manipulation technique for Internal Derangement of TMJ is a highly effective therapy, especially for primary cure, not only to achieve unlock (reduction of displaced disc), but also to improve its pathological condition (stretch of parajoint soft-tissue, enlargement of joint space, improve of joint circulation). Accordingly, repeated exercise such as manipulation (self-traction therapy) can bring about softening and relaxation of the joint capsule, and is effective as a physical and kinesitherapy for internal derangement of TMJ.
We treated internal derangement of TMJ mainly using self-traction therapy. In this study, we evaluated self-traction therapy for internal derangement in the second and third decades, because they are more simply diagnosed as closed lock or unlock than older decades.
The 88 cases of internal derangement which included 45 cases of closed lock, 18 cases of intermittent closed lock were treated with self-traction therapy. The combination therapies were pumping manipulation or pivot-type occlusal splint and arthroscopic or open surgery. The cases were treated after unsatisfactory progress by treatment with self-traction therapy for several weeks. 30 cases of closed lock achieved unlock, 5 cases of intermittent lock disappeared and 8 cases decreased the state of locking, due to repeated exercise of self-traction.

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This study was undertaken to evaluate the influence of the resection of temporal muscle upon the growth and development of the mandible.
The Materials consisted of 24 Wistar strain rats (male, 28 days old).
The resection of the left temporal muscle was performed in the experimental group, which was sacrificed 8 weeks after the operation.
Morphological measurements and soft X-ray analysis were carried out.
The results obtained were as follows;
(1) The side shift of the mandible was not seen when the mouth was closed in experimental group.
(2) The size of the coronoid process was significantly smaller in the operated side. The condylar process became thinner from the neck region and its configuration changed. In addition, the angular process region showed a downward curvature, and there was a difference in the position of the apex of the angular process between operated and non-operated side.
(3) The incisor teeth were inclined to lingual in the experimental group.
From these results, the resection of the temporal muscle on one side that made the muscle function asymmetric influenced the growth of the whole mandible.

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Pathogenic changes of muscle pain in temporomandibular disorder (TMD) patients are unknown. Local ischemia, however, seems to be one of the important factors of the muscle pain. Recently, the pharmacologic effect of centrally acting muscle relaxant, with vasodilation actions, on muscle pain has been reported. We investigated blood flow changes at rest of the masseter muscle in anesthetized rat during pre- and post-injection of NK433 (a new centrally acting muscle relaxant: Lanperisone hydrochloride) using a laser Doppler meter. Responses of post-exercise hyperemia induced by tetanic contracture were also studied.
The results showed that the blood flow at rest of the masseter muscle increased for two minutes after injection. The half-time period of post-exercise hyperemia induced by tetani contraction was significantly shortened until 30 minutes after injection.
These results suggested that a therapeutic effect of NK433 on TMD muscle pain might be available with its increasing blood flow action in the skeletal muscle.

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The condylar surface form of 45 edentulous patients, 15 males and 30 females were observed by using a zonogram. None of the patients presented any symptom of teniporomandibular disorder as a chief complaint. The incidence of abnormality of condylar surface form, and the factors which are concerned with the manifestation of abnormality of condylar surface form were investigated.
(1) Abnormality of condylar surface form was recognized in 71% of patients. The group with abnormality of condylar surface form on both sides comprised 66% more cases than that with the incidence on one side.
(2) In 52 joints that had abnormality, erosion was recognized in 60.6%, flattening in 22.7%, osteophyte in 10.6% and concavity in 6.1%.
(3) The incidence of abnormality of condylar surface form was higher in the group of over 70-year-old patients than in the group of less than 69-year-olds (level of significance 0.01%).
(4) The incidence of abnormality of condylar surface form was higher in the group with joint noise than in the group without joint noise (level of significance 4%).
(5) The incidence of abnormality of condylar surface form was higher in the group with poor denture stability than in the group, with good stability (level of significance 2%).
(6) The factors which were not recognized as relevant to manifestations of abnormality of condylar surface form, were sex, edentulous term, tenderness on palpation, years in use of present denture, retention, free way space, teeth material, attrition, upper denture movement at occluding, removal of denture during sleep, maximum opening distance, habitual masticatory side and deviation on opening.

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Thirty-four patients (37 TMJs) having permanent disc displacements were treated with pumping and manipulation followed by occlusal therapies.
The results were as follows;
(1) Through pumping and manipulation, twenty-three discs (62%) were reduced, but after occlusal appliance therapies, only 6 discs (16%) retained the normal positions and 3 discs (8%) were reducible on mouth opening.
(2) Patients with the normal disc positions showed wider range of mouth opening and shorter treatment periods than the others.
(3) Severe disc displacement and fibrous adhesion in upper joint spaces showed significantly lower possibility in repositioning the normal disc position. On the other hand, age, lock terms and opening range before treatment were not significant factors.
(4) New occlusal positions were determined in 16 patiens (47%) and occlusal therapies including restorative treatments and occlusal equilibration were performed in 25 patients (74%). Mainly single crowns and small-unit bridges were placed as final restorations.

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We analyzed the morphology of the condylar head of the human temporomandibular joint without symptoms by using CT. The normal condylar heads of 120 people were evaluated. There was no correlation between the morphology of condylar head and age. However, the male was significantly wider than the female at the maximum cross-sectional area of the condylar head, and longer both on the long and short axis. The morphology of the female was more round in shape than that of the male on the condylar head. On the other hand, the horizontal condylar angle was the same in the male and female, that is about 18 degrees. The left side morphology was bigger than the right side for loth sexes, and it was considered that there might be specific differences between right and left sides. Also, the lateral size of the skull did not influence the morphology of the condylar head. It was considered that these results misht be one of the landmarks of the morphological analysis of patients with temporomandibular joint disorders.

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Traumatic synovitis of rat temporomandibular joint in 8 weeks Wistar male rats was induced by condylar hypermobility (mouth opening of about 20mm) ten times repeated a day for ten days. The synovitis was mostly observed in the anterior synovia of the upper joint. After the treatment, the pathological changes of the synovitis were observed at 6, 8, 10 and 20 weeks. The results were as follows;
(1) At 6 weeks, synovitis characterized by multiple layers of synovial cells, dilated vasculature and synovial adhesion was frequently noticed.
(2) The frequency and degree of synovitis decreased with time and the synovitis and adhesion were not observed at 20 weeks after the treatment.
(3) Transition of the synovitis into fibrosis occured in the anterior synovia, in which synovitis was observed frequently.
(4) From the results, it was suggested that the synovial adhesion will disappear maturally.

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Many operation techniques have been used for treatment of internal derangement of the temporomandibular joint (TMJ). We developed an arthroscopic disc suturing technique of the TMJ and, at the 8th symposium of the Japanese Society of the Temporomandibular Joint, had the opportunity to report the clinical results. To comprehensively assess the effectiveness of the technique, not only the surgeon's objective judgement, but also the patient's subjective evaluation are required. Therefore, we studied whether or not patients who underwent the surgery were satisfied with their postoperative status.
58 joints of 40 patients were studied, including 14 males and 26 female (age: 17-74 years; mean 27.9 years). They were followed up for at least one year (mean: 3 years and 9 months; range: one year and 4 months-6 years and 7 months). The mean range of mouth opening was significantly improved from 34.4mm before the operation to 40.7mm after surgery. Arthralgia was completely relieved in 71.8% of the cases, noise in the joint was perfectly resolved in 78.4%, and no disturbance was found in the daily life of 57.5% after surgery. The overall improvement rating was 78.7% based on assessment of the function we devised and the patient's degree of satisfaction.

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The purpose of the study is to clarify the relationship between disk or retrodiscal connective tissue perforation of the temporomandibular joint (TMJ) and morphologic alteration of the mandibular fossa. Sixty-one TMJs were prepared for the study (male: 30 joints; female: 31 joints). The mean age of the cadavers was 74.5 years. The mandibular fossa and articular disc of TMJ were studied by macroscopic observation and measured the thickness of the thin-net area of the fossa was measured.
The Macroscopic findings were as follows: Eleven discs were perforated, 50 were non-perforated; the size of perforation was large in four, medium in two and small in five; the smallest thickness of bone at the mandibular fossa was 2.5mm on average in the perforated group, and 0.8mm in the non-perforated group.
Our results indicate that increases of mechanical stimulation may cause an increase of bone thickness at the mandibular fossa because of an incomplete shock absorber function due to the disc or retrodiscal connective tissue perforation.

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The success of treatment for TMJ ankylosis depends on the surgical procedure and postsurgical physiotherapy. Physiotherapy is specially important to prevent reankylosis. At present, there have been only a few long-term follow-up studies on postsurgical treatment using current by available exercisers. Furthermore, the outcome of such postsurgical physiotherapy is below the acceptable clinical standards and patients have to undertake frequent long-term and painful experience using the exercisers. For these reason, we devised a new exerciser (HU-OS II) which controls pain and gives a clear idea of interincisal mouth opening distances during active exercise. We applied the HU-OS II to 4 cases of TMJ ankylosis. In these 4 cases, who were followed for 5-11 years after operation, the interincisal mouth opening distances these were 34-42mm.

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The purpose of this study was to investigate the clinical effects of treatment by using an occlusal splint in juvenile temporomandibular disorders. The subjects were 30 young patients, who were aged 12-18 years.
The results were as follows;
1. The results of the first examination
(1) The most frequent of the chief complains of TMJ (Temporomandibular Joint) were TMJ pain (21 subjects, 70.0%) followed by TMJ noise and trismus.
(2) The period from the first significant symptoms of TMJ to the first examination was usually within three months.
(3) As to the present status in the first examination, 13 subjects (43.3%) complained of TMJ pain combined with TMJ noise and trismus.
(4) The frequency of the individual classifications according to The Japanese Society for Temporomandibular joint disorders (1986), were 19 subjects (63.3%) suffered from Type III, 7 subjects (23.4%) from Type II, 2 subjects (6.7%) from Type I and Type I+II.
2. The results of treatment
(1) The results and the effects of the splint treatments were examined to ascertain the improvement ratio. TMJ pain was rapidly improved within 10 weeks. TMJ pain was completely improved with in 18 weeks and masticatory muscle pain in 14 weeks.
(2) TMJ noise was less readily improved and 3 subjects were able to gain no improvement after a period of 24 weeks.
(3) Trismus was completely improved in 14 weeks.
(4) The average length of time for trismus improved being 5.6 weeks. The differences in length of time between the averages of improved period on trimsus and TMJ pain and the averages of improved period on trismus and TMJ noise were statistically significant (p<0.05). After conclusive study, results showed that cases that involved trismus took a greater length of time to improve.

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The authors evaluated the clinical effect of some kind of occlusal splint therapy for the patients with each types of temporomandibular joint (TMJ) disorders and investigated the relationship between the wearing time of splint and the clinical effect of this therapy. The subjects were 153 patients (113 females and 40 males) who were treated by occlusal splint therapy in our chinic from January 1990 to December 1991.
According to the classification of Japanese Society for TMJ, all patients were classified into four types of TMJ disorders. 80 cases were type III, 13 cases were type IV, 12 cases were type I and 8 cases were type II. Stabilization splint was applied to 101 patients, resilient splint to 38 patients, anterior repositioning splint to 27 patients, disc recapturing splint to 12 patients and another type of splint to 6 patients.
The patients, who had used the occlusal splint for over two weeks, were examined to estimate the clinical effect after the completion or the stop of this therapy. The effect of stabilization splint therapy is excellent in 11 cases, good in 41 cases, fair in 9 cases and poor in 27 cases, therefore, the overall success rate of this splint therapy is 68.5% (61 of 89 cases). The success rates of resilient splint and anterior repositioning splint were 83.3% and 76%, respectively, but both success rates included much more fair cases than that of stabilization splint. The disc recapturing splint showed the lowest success rate, 66.7%. In each splint therapy, the cases wearing less than 8 hours per day showed lower success rates, on the other hand, the cases wearing more than 16 hours per day showed higher success rates. However, it suggested that the longer wearing time of the splint did not always give good results for the patients who suffered from TMJ disorders for more than one year.

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[in Japanese]

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This is a case report of a lateral chin deviation with the temporomandibular joint and the referred symptoms. The patient was a 26-year-old man complaining of right TMJ pain and a strange feeling around the area of the head, neck, shoulders and arms.
Clinical examination revealed that the chin was shifted 5mm to the left, there was class III molar occlusion and lateral crossbite at the left side. The TMJ symptoms were pain and crepitus on the right and clicking on the left. Tenderness was detected on parts of TMJs, anterior temporalis and sternocleidomastoid muscles.
The tomographic and arthrotomographic images of sagittal sections showed hyperplasia of the right condylar neck and there was anterior disc displacement with reduction of the left TMJ. Therefore, this case was diagnosed as an Angle class III lateral chin shift with temporomandibular arthrosis type I+type III.
It was then confirmed that mandibular shift correction relieved the patient's TMJ symptoms. The lower first premolars were extracted and multi-brackets were directly bonded. For orthodontic occlusal reconstruction, a splint was used to keep the jaw in position. As a result, the patient's TMJ symptoms disappeared.
Occlusal reconstruction by orthodontic treatment, which moves the teeth slowly, takes time but is thought to be effective for seeking the adaptation of the neuromuscular system on the stomatognathic area.

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In order to clarify the clinical significance of morphological bone changes of the mandibular condyle in temporomandibular disorders, the authors clinically studied the relationship between radiographic bone changes and the internal derangement in 1, 120 patients. The morphological bone changes according to radiograms taken by lateral oblique transcranial projection, orbit-condyle projection and orthopantomography were classified into seven groups: erosion, osteophyte, eburnation, flattening, deformity, concavity and sclerosis. As the condition of temporomandibular disorders, the classification of temporomandibular disorders of the Japanese Society for the Temporomandibular Joint (1987) was subdivided into ten types. The ten types are: Type I (masticatory muscle disorders without internal derangement), type II (micro traumatic synovitis without internal derangement), type IIIC+ (internal derangement; disk anterior displacement with reduction), type IIIC- (internal derangement except disk anterior displacement with reduction; disk lateral displacement with reduction, etc.), type IIIL (internal derangement; closed lock), type IVo (osteoarthrosis with masticatory muscle disorders without internal derangement or no symptoms), type IVp (osteoarthrosis with micro traumatic synovitis without internal derangement), type IVC+ (osteoarthrosis with internal derangement; disk anterior displacement with reduction), type IVC- (osteoarthrosis with internal derangement except disk anterior displacement with reduction), type IVL (osteoarthrosis with closed lock).
The results were as follows;
(1) In 1120 patients, osteoarthrosis was found in 120 patients (10.7%), and the female and significantly older (p<0.01) patients were dominant.
(2) osteoarthrosis was significantly predominant in patients with disk disorders, especially closed lock (p<0.01).
(3) The frequency of radiographic bone changes were as follows: erosion; 82 (34.7%), osteophyte; 50 (22.8%), eburnation; 28 (12.8%), flattening; 23 (10.5%), deformity; 22 (10%), concavity; 13 (5.9%), sclerosis; 1 (0.5%).
(4) Erosion was significantly predominant in patients of type IVp (p<0.05), and flattening was significantly predominant in patients of type IVC- (p<0.05).

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The purpose of this study was the evaluation of TMJ dysfunction symptoms in orthodontic patients by questionnaires and study casts.
Data was obtained from 258 orthodontic patients (97 males and 161 females) with a mean of 15.0 years, who visited the orthodontic clinic of Niigata University Hospital from 1991 to 1995. 172 (over 12 years old) of all 258 patients were divided into a general orthodontic patients group and an orthognathic surgery patients group with orofacial deformities.
The results were as follows;
(1) The incidence of TMJ dysfunction symptoms was 28.7% of the total sample, and no significant difference of incidence by sex were recognized.
(2) Both joint noise and disturbance of jaw movement were found in 29.7%.
(3) The incidence of TMJ dysfunction symptoms increased with age and was 60.7% in patients over 20 years old.
(4) The questions about life environment and habits showed that there were 5% significant differences in unilateral mastication, trouble in mastication, trouble in mastication of hard food, stiff shoulder, inclined posture, and insomnia.
(5) Over 12 years old, a significantly higher incidence of TMJ dysfunction symptoms was found in orthognathic surgery patients than in general orthodontic patients.

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Reported herein are three patients who were sent to our department in the past 12 years by another hospital with trismus as the chief complaint. They were diagnosed with tetanus and treated successfully. Although the incidence of tetanus in Japan has significantly decreased in recent years it remains a highly life-threatening disorder. Dentists and oral surgeons who encounter trismus as an initial symptom should be aware of the clinical symptoms and conditions, because this disease requires early treatment.

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In order to clarify the clinical significance of morphological bone changes of the mandibular condyle, the authors clinically studied the relationship between radiographic bone changes and clinical findings in 166 joints of 120 patients with osteoarthrosis of temporomandibular joint. The bone changes according to radiograms taken by lateral oblique transcranial projection, orbitcondyle projection and orthopantomography were classified into seven groups: erosion, osteophyte, eburnation, flattening, deformity, concavity and sclerosis. As clinical findings, joint noise (crepitus, click), pain (joint pain, muscle pain) and maximal interincisal opening distance were chosen.
The results were as follows;
(1) 32 joints (19.2%) of 166 joints had neither joint had noise nor pain.
(2) 73 joints (44%) in 166 joints had joint noise, and in the 73 joints with joint noise 47 joints (64.4%) had crepitus.
(3) Erosion was largely found in the mandibular condyle with booth single bone change and multiple bone changes.
(4) In joints with erosion, many joints were without joint noise and with pain. These results indicate that erosson is the most predominant radiographic finding with pain when the temporomandibular joint is out of balance.

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