This study was conducted to investigate the nature of prevalence of temporomandibular joint (TMJ) disorders in adult students by means of the evaluation of the intraarticular pathologic status with MRI.
Thirty-eight students in the Dental Technicians School, Hiroshima University School of Dentistry were used as the subjects. The subjects consisted of 13 males and 25 females with a mean age of 22-year 2-month old (range; 19-45). Intraarticular pathologic status was classified into six stages according to Wilkes and Schellhas criteria based on the degree of disk displacement and deformations of the disk and condyle on the MR images. The following findings were obtained.
1. TMJ disorders were found in 42% of all the subjects, or in 35% of all the joints.
2. Anterior displacement of the disk was detected for 15 subjects (39%) or 23 joints (31%). Among these subjects, seven subjects presented unilateral disk displacement, and bilateral disk displacement was found in the remaining eight subjects. Reducible disk displacement was observed in 15 joints (65%) among 23 joints with disk displacement, whereas 8 joints (35%) exhibited disk displacement without reduction.
3. Disk deformation was recognized in seven and seven joints (47% and 88%) out of 15 and 8 joints with reducible and irreducible disk displacements, respectively.
4. Intraarticular pathologic status for the internal derangement was as follows. Stage 0; 49 joints, Stage I; 7 joints, Stage II; 6 joints, Stage IV; 9 joints, and 4 joints were unclear.
It was shown that prevalence of TMJ internal derangement was 39% in adult students.
These findings indicated an importance of special attention to these asymptomatic subjects, if they undergo dental treatment, in order to prevent an onset of the latent pathologic status in the TMJ.

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A retrospective study was performed using two treatment groups of unilateral TMD patients in order to evaluate the influence of the occlusal factors to the treatment results.
One group comsisted of 193 patients treated with the procedures including a stabilization type appliance and/or an occlusal adjustment procedure, and the other group consisted of 189 patients treated with the other procedures without stabilization appliance or occlusal adjustment.
The factors investigated were as follows: Angle classification II or III, overbite over 5mm, overjet over 5mm, lost of molar support, decreased vertical dimension, premature contact, occlusal contact on nonworking side, undesirable anterior guidance, history of trauma to the mandible, experience of orthodontic treatment, and night bruxism.
The treatment procedures, except for stabilization type appliance therapy and occlusal adjustment, included education for life style, medication, joint moving exercise, muscle stretching exercise, muscle loading exercise, repositioning type appliance therapy, pivoting type appliance therapy, night guard, disk repositioning manipulation, gum chewing exercise, psychological counseling, and acupuncture.
The results suggested that either the stabilization type appliance treatment or the occlusal adjustment procedure for the purpose of avoidance or improvement of occlusal problems were not necessary to improve the symptoms of TMD patients. The logistic regression analysis suggested that the factor other than the investigated factors might be associated with maintaining the symptoms.

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This study was conducted to evaluate the movement of a disc with temprormandibular joint (TMJ) dysfunction. In this paper, fast-scan MR images were compared with spin echo images in TMJs at static closed and maximally opened mouth, and characteristic of fast-scan MR imaging was examined during incremental mouth opening and closing. The subjects wered of 8 patients (2 males and 6 females) with TMJ dysfunction, and their age ranged from 19 to 35 years with a mean age of 25.9 years. Of these 8 patients, 7 had unilateral 1 bilateral and TMJ dysfunction. Sixteen TMJs of 8 patients was imaged by a whole-body MR imager (SIGNA, GE Medical System) operating at 1.5 Tesla with a dual 3 inch receiver coil. To increase contrast, the on-resonance binomial magnetization transfer contrast (MTC) pulse was applied to gradient recalled acquistion in a steady state (GRASS) in fast-scan MR imaging. A series of sequential images were obtained with opening and closing mouth, using an opening device. The fast-scan MR images had not high resolution in appearance of discs and condyles in some TMJs compared with spin echo images. However, in movie mode the pertinent joint structures such as disc, condyle, posterior band, and masticatory muscles were clearly delineated. The fast-scan images demonstrated two directions of deformity of disc associated with incrementally opening mouth in the patients with anterior disc displacement.

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Mandibular border movements were recorded at the incisal point for 168 patients with internal derangements of the TMJ, which were ascertained by MR images. On the basis of MRI findings including bilateral TMJs, the status of the discs were classified as reducing, nonreducing and sideways disc displacement. The characteristics of border movements and frequencies of restricted movement in various types of disc displacement were investigated. In addition, a follow-up study was undertaken to examine the transfer frequencies from reducing to nonreducing conditions of the disc.
The results were as follows.
1) There was no difference in mandibular movement between unilateral and bilateral cases in patients with internal derangement of the TMJ.
2) In unilateral cases, reducing cases indicated only unilateral restriction of the mandibular movements, while nonreducing ones chiefly bilateral restriction. These tendencies were also true when reducing and nonreducing groups included bilateral cases.
3) Restriction pattern of mandibular movements in patients with sideways disc displacement was rather similar to that of nonreducing cases as compared with reducing cases.
4) Affected side of movement restriction, instability of maximum opening position, and W-shaped limitation of opening range enhanced to evaluation of TMD conditions, especially disc displacement.
5) Six percent of 62 patients in the reducing group, including sideways disc displacement were transfered to the nonreducing, roup during the follow-up period.

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The purpose of this study was the measurment of skin dose with thyroid gland, both sides of temporomandibular joint (TMJ) and eye in the X-ray examination of TMJ. The methods of X-ray examination were fluoroscopy, conventional lateral tomography, arthrotomography and arthrofluoroscopy. Objective cases were 37 patiants diagnosed with TMJ disorders clinically (10 males and 27 females).
Following results were obtained.
1. The exposure time of fluoroscopy at the arthrotomography was approximately 1.6-4.1 minutes.
2. The skin dose was 0.58-2.88mGy on the objective side of TMJ from the fluoroscopy at the arthrotomograpic examination. On the contrast, the skin dose of objective side of TMJ was 0.15-0.24mGy in fluoroscopy without contrast media.
3. The skin dose of exposure area from the fluoroscopy was measured by means of phantom, and it was 6.43mGy/min.
4. The skin dose at TMJ from the arthrotomography and tomography was respectively 15.6mGy and 13.6mGy/exposure.
5. From the arthrotomography of TMJ, skin dose at TMJ of objective side which suited at the exposure side was 62mGy.

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This study was performed to evaluate the significance of lateral preference in mastication and test the usefulness of the examining method. One hundred two subjects in their twenties were selected from among the students and staff of Faculty of Dentistry, Kyushu University. Subjects were asked about chewing side preference before and after simulative mastication by themselves. The frequency of awareness of preferred chewing side was significantly increased after simulative mastication (68% to 81%). The ratio of chewing side preference was described by using a visual analog scale and the ratio of preferred chewing side to non-preferred chewing side was about 70%. The results of the questions after simulative mastication highly corresponded to the results of the cotton role test. The query after simulative mastication could be useful to detect the preferred chewing side of a patient. However, investigating its reliability should be further investigated to establish the examining method of the preferred chewing side.

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This study was performed to investigated the effect of wearing an occlusal splint on the pattern of occlusal contact in the intercuspal position. Ten healthy young adults were randomly selected from among the 1st and 2nd year undergraduate students of the Faculty of Dentistry. Five out of ten subjects were placed in the control group, and the other five in the a splint group. A full maxillary stabilization splint made of heat-cured acrylic resin was worn by each splint-group subject for 9 hours. Before and after wearing an occlusal splint, the presence or absence of an interocclusal contact of each tooth was examined using mylar shim shock in the intercuspal position that a subject performed. Bite feeling of a subject was also examined using a visual analog scale. The examination was performed by blinded examiners over the period of 2 hours after removing a splint. The analysis of the proportion of agreement between the control and splint groups showed that the pattern of occlusal contact and bite feeling significantly changed after wearing an occlusal splint (p<0.05). However, the pattern of occlusal contact recovered within one hour, and bite feeling within 2 hours in all splint-group subjects. Therefore, irreversible change of the pattern of occlusal contact does not occur by the intermittent use of an occlusal stabilization splint. In other words, the constant use of the splint may cause a permanent change of the pattern of occlusal contact, suggesting careful consideration to its clinical application.

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In order to know how to diagnose and treat painless temporomandibular joint sounds, a questionnaire was sent to specialists of TMD who were members of the Japanese Society for Temporomandibular joint. Of the 123 specialists of TMD who were sent a questionnaire, 97 responded, for a response rate of 78.9%.
Seventy point one percent of the respondents classified sounds for treatment, ex.) click due to disk anterior displacement with reduction, crepitus due to disk anterior displacement without reduction, eminence click, etc. The classification varieel greatly. Nine point three percent of respondents “always” treated the painless click due to disk anterior displacement with reduction, 86.8% “sometimes”, and only 4.1% “never” treated this click. Eighty-five point seven percent of “sometimes” respondents treated this click when of very uncomfortable. Eighty-three point three percent treated when of intermittent closed lock, 64.3% treated when mandibular movement was hesitated. The reason why this click was not treated was mostly that a long-term result of treatment was miserable sometimes. Forty one point two percent of respondents did not regard this click as a pathologic sign or symptom of TMD.

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It was suggested that mandibular movement disorder is closely related to the TMJ of masticatory muscle in TMD patients. However, this relationship has not been confirmed.
The purpose of this study was to quantitatively evaluate the mandibular movement in TMD patients in order to elucidate the relationship between abnormalities of the TMJ or masticatory muscle and mandibular movement disorder.
A total of 103 joints, consisting of 94 TMD joints as subjects and 9 normal joints as controls, was selected. The maximum translation and rotation of condylar movements was measured using the apparatus developed by Nagata et al. The subjects were divided into 6 subgroups, and each volume of maximum movement was statistically compared among the groups employing the discrimination analysis.
The conclusions were as follows:.
A marked limitation of movement was observed in the groups with abnormal TMJ.
77% of anterior disk displacement with reduction (ADD/wr), 16% of anterior disk displacement without reduction (ADD/wor), and 50% of osteoarthrosis were within normal limits in the movement volume, some of which involved an abnormal TMJ without limitation of movement.
There were no significant differences in ADD/wr in comparison with the normal group.
Both translation and rotation movements tended to reduce in ADD/wor compared to the normal group.
There was no relationship between PD and hypermobility of TMJ.
From the results, it was suggested that limitation of condylar movement related to TMJ disorders, and each disorder has a different feature of limitation.

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In this study, statistical methods about the relationship between with three-dimensional mandibular movements, clinical findings and the disc perforation of 36 patients that were diganosed as anterior disc displacement without reduction, were investigated by the video-fuluoroarthrography.
As a result, an obvious relation was not confirmed between disc perforation and mandibular movements. Also the condylar deformity was the relational factor of disc perforation, and the odds ratio was 9.0.
In the result, to diagnose disc perforation, yet it was thought that arthrography was indispensable.

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The purpose of this study was to observe disc repair and investigate reestablishment of the transformed joint by MRI after nonsurgical treatment of condylar fractures.
The study was based on 9 unilateral and 6 bilateral condylar process fractures treated in 15 patients. The patients were 11 to 81 years old (mean: 43.5 years). There ware condylar head fracture were 14 joints, condylar neck fracture in 5 joints, and subcondylar fracture in 2 joints.
Conservative treatment consisted of early jaw-opening exercise, elastic traction, intermaxillary fixation, and control of the occlusion.
After treatment, morphologic changes of the condyle were found in 20 joints. However, in all but was 1 case, pain-free mouth opening with an interincisal distance greater than 40mm were obtained.
Condyles were situated at the glenoid fossa or articular eminence when the jaw was closed. All but 1 disc were observed at the superior position relative to the condyle when the jaw was closed. As for jaw movement, all discs sympathetically moved with condyles.
In these patients, satisfactory clinical results were obtained. Shortening of the ramus height was brought about by dislocated or displaced condylar fracture, but it was improved by deformed condyle were situated at the lowest point of the articular eminence after healing. The remodeling of the fractured condyle proceeded to a form that adapted well to new location. The repaired discs were located over the deformed and/or displaced condylar head in the jaw closed position and moved sympathetically with the condyle during jaw movement.

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The purposes of this study was to deduce a typical MR image of the temporomandibular joint with the disc perforation from evaluation of a number of similar cases and to investigate the predictability of MR imaging of disc perforation.
Material and methods: The first pair of subject groups used for comparison were 50 TMJs with perforation and 50 TMJs without perforation. The second pair of compared groups were 10 TMJs with perforation and 10 TMJs without perforation. All TMJs were examined by MR imaging at 0.3 Tesla (MRP-7000 HITACHI MEDICO, Tokyo). The case of disc perforation was judged by double-contrast arthrotomographic examination. Typical MR images of the TMJ with disc perforation were determined from the first pair of subject groups. The second pair of subject groups were used for determination of diagnostic accuracy on the basis of the typical MR findings of perforation discs, such as sensitivity, specificity, and positive and negative predictive values.
Results: The typical MR findings of a perforated disc had marginal proliferation of the condyle, surface irregularity of the area ranging from eminence to fossa and disc deformation such as biconvex. Diagnostic accuracy of the findings was 75 to 80 % from a single finding and 85 % from multiple findings.

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Previous studies have shown a relationship between mandibular positional changes in maximum jaw opening and craniofacial morphology. The purpose of this study was to evaluate the mandibular positional change in maximum opening with measurement of both incisor and condyle points, and to analyze the correlation between the positional change and the craniofacial morphology. The subjects were 125 untreated orthodontic patients (42 males and 83 females, mean age: 15.4 years) who have no history and presence of temporomandibular disorders. Lateral cephalograms were obtained from each subject in the intercuspal position and in the maximum opening position. Six variables of the positional change of the mandible and 54 cephalometric variables were measured by using a computerized cephalometric system. Methodological errors were 0.14mm in linear values and 0.27 degrees in angler values. To reduce the number of variables and to make use of existing correlations, factor analysis determined 3 factors for the positional change of the mandible were determined by factor analysis. Factor 1 (explaining 51.1% of variance), factor 2 (30.9%), and factor 3 (12.4%) could be defined as the posterior direction of incisor opening, the amount of condylar movement, and the amount of incisor movement, respectively. Significant correlations (p<0.01) were observed in factor 1 with GoGn/SN (r=0.44) and SNA (r=0.40), factor 2 with SE (r=0.57) and SN/NBa (r=0.47), and factor 3 with SNB (r=0.64), SL (r=0.67) and facial angle (r=0.57). These results suggested that opening direction of incisors and the amount of condylar movement as well as the amount of incisor movement should be considered when describing the mandiblar position in maximum opening, and that hyperdivergence of the face and maxillary retrognathism correlate with the opening direction of incisors, and the anteroposterior position of the temporomandibular joint correlates with the amount of condylar movement.

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