We investigated the changes of signs and symptoms in 30 patients with anterior disc displacement without reduction of the TMJ who had refused any treatment. The results were as follows:
(1) Average maximum mouth opening increased from 31.1mm to 37.1mm in 12 months.
(2) Crepitation was noted in 7 patients at first visit, and in 7 patients at the 12-month follow-up.
(3) The number of patients with pain of the TMJ decreased from 24 to 11 in 12 months.
(4) The number of patients with pain of the masticatory muscles decreased from 14 to 2 in 12 months.
(5) The changing of the TMJ dysfunction at the 12-month follow-up showed no dysfunction (7 patients), improved (15 patients), no change (8 patients).
These results show that we should take natural alleviation of the symptoms into consideration when anterior disc displacement without reduction of the TMJ is treated.

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The cranial outline in the transverse plane (plagiocephaly) is related to facial types or occlusion types. The shape, position and angulation of the condylar head is also affected by differences in sex, ages and the type of occlusion. There have been no research reports on the relation between plagiocephaly and condylar angulation.
The authors investigated the relation between the direction of cranial deformity and the condylar angulation in the transverse plane using submentovertical cephalograms of 23 cases.
The present findings indicate that the condylar angulation of the flattened side of the cranium showed a significantly smaller degree of angulation than that of the non-flattened, opposite side (p<0.01).

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To evaluate the nature of pain at pressure pain threshold (PPT), we measured the intensity of the pain on the visual analog scale (VAS) at pressure pain reception in the maxillofacial region. Fifty volunteers (men: 13, women: 37) with no symptoms of temporomandibualr disorders were examined in the seven setting measurement points of the maxillofacial region. The subjects PPTs were measured using the algometer at a constant rate of 500g/cm²·s and the intensity of the pain on the VAS at that time was recorded. The distance of the mark from the left end of the scale was defined as the VAS score.
The Results showed that the VAS scores in the points of the forehead, the anterior bundles of the temporal muscle, the posterior margin of the mandibular ramus and the Libman's point were significantly different from those of other measurement points. Among of the points in the inferior and mid portion of the masseter muscle and the lateral pole of the condyle, the VAS scores were not found to be significant ly different. In addition, from the significant correlations of the VAS scores in all measurement points, it is considered that a person with higher VAS score of the pain at pressure pain reception is inclined to evaluate the VAS score high in any measurement points in the maxillofacial region.

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To epidemiologically investigate the background of the increase of patients with temporomandibular disorders (TMD) in recent years, the prevalence of subjective temporomandibular joint (TMJ) symptoms was examined by a questionnaire in more than 2, 000 first-year university students in every year from 1989 to 1993. There was no significant difference in the incidence of subjects with awareness of TMJ sounds and limitation of mouth opening during the five years. There was also no significant difference in the incidence of subjects with pain at wide mouth opening, except for 1989. The incidence of students who were aware of only one symptom or who infrequently reported TMJ symptoms slightly decreased during the five investigated years, whereas those who were aware of three main symptoms or who frequently noticed TMJ symptoms did not change.
These findings suggest that there was no change in the number of young adults with awareness of TMJ symptoms in recent years, contrary to the increase of the number of TMD patients.

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We observed 121 temporomandibular disorder patients who complated Cornel Medical Index questionnaires in order to investigate the corelation between temporomandibular disorders and psychological factors. All 121 patients were classified into 4 (I-IV) types by means of the criteria proposed by the Japanese Society for the Temporomandibular Joint. In addition, all 121 patients were classified into 4 (I-IV) categories in CMI.
As a result, the type I of temporomandibular disorder patients significantly showed a tendency of shifting into CMI categories III and IV, compared with other types (II-IV) of temporomandibular disorder patients. It is suggested that the type I of temporomandibular disorder patients had many psychological factors.

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Surgical reduction to the degenerative TM joints varies. Although arthroscopic and open surgical methods are applied, there is no clearly defined criteria whether to remove or to preserve the distorted disk. In the present study, the postoperative results of the disc-repositioning method and disc-removal method were been evaluated.
The classification of the American society of TMJ surgeons was applied to 12 degenerative joints, postoperatively. These joints were classified as stage III 5 joints, stage IV 3 joints and stage V 4 joints. The cases of stage III and stage IV underwent disc-repositioning surgery. And cases of stage V underwent discectomy with earcartilage grafting. More than six months afta the operation, the following results were obtained: disc repositioned stage III-5 joints were excellent, disc repositioned stage IV-of the 3 joints, 2 joints were excellent and 1 joint good. Of the 4 Disc removed stage V 3 joints were excellent and 1 joint good.
Reviewing the follow up results, there is minor improvement of maximal open range and VAS among the stage IV joints recognized. From these results, the need of the disc removal method among stage IV joints is suggested.

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The morphology of the temporomandibular joint (TMJ) in eight human fetuses, which ranged from 19 to 25 weeks of gestation (measuring 158mm to 213mm in crown-rump length), were investigated with light microscopy and scanning electron microscopy (SEM). One joint obtained from each fetus was sectioned in the sagittal, coronal, or horizontal plane. Each section was 5 microns thick and every fifth section was stained with hematoxylin and eosin or Elastica van Gieson stain, and neighboring sections of the same specimen were observed with SEM. It was the purpose of this work to investigate whether or not there was an influence on the development of the TMJ by the movement of the mandible in fetal stages. In this series, calcification in the area of attachment of the lateral pterygoid muscle to the condyle was earlier than that in other condylar regions. In the lateral and medial area of the lower joint cavity of the temporomandibular joint, the cavity space seemed to develop from tearing between the disk and condyle. In the SEM findings, the upper collagen fibers of the disk were dense and there were few of fibro blasts while the lower fibers of the disk were very sparse, and there were more cellular elements. It is suggested that functional adaptability is earlier in the upper region of the disk than the lower one. The surface of the condylar head had crinkles on its top area. In addition we observed a condensation of the nucleus in some parts of condylar proliferating portion in the hematoxylin and eosin stained findings. These findings suggest that there is a possibility of “apoptosis” in development of the temporomandibular joint.

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Mandibular opening movement is composed of a combination of condylar rotation and translation. The purpose of this investigation was to study the relationship between condylar rotation and translation during opening movements in order to clarify whether these two moving components are available for diagnosis of temporomandibular (TM) joint disorder.
Twenty seven subjects without signs or symptoms of TM joint disorders (normal group) and 20 subjects with at least unilateral clicking joint (TMD group) were examind regarding with the amount of condylar rotation and translation and the relationship between these two moving components utilizing computerized axiographs. Anterior complete disk displacement with reduction was confirmed by magnetic resonance imaging. The amount of condylar translation of the TMD group was longer than that of the normal group in the opening movement, while the amount of the condylar rotation was not significantly different in these two groups. It was suggested that the excessive translation in the TMD group resulted from looseness of the capsule and lateral ligament. Furthermore, results indicated a highly linear relationship between condylar rotation and translation except for the terminal end of the opening movement in the normal group. The final stage of the opening movement in the normal group mostly consisted of condylar rotation. On the other hand, the opening movement in the TMD group started with rotation movement predominance, and finished by the same ratio of rotation and translation movements.
It was concluded that the examination of the relationship between condylar rotation and translation can be useful for a diagnosis of TM joint dysfunction including loose ligament.

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Isberg, et al (1987) reported lingual numbness and speech articulation impairment associated with temporomandibular joint disk displacement. They thought it occurred when the lingual nerve passes through the lower head of the lateral pterygoid muscle.
TMD (temporomandibular disorder) patients were investigated in relation to paresthesia of the tongue by using TMD questionnaires in 1992. 18 of 503 TMD patients had an impairment in tongue sensitivity and 1 patient seemed to have the same symptoms as those in Isberg's report.

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MR studies of 502 temporomandibular joints were performed in 251 patients with TMJ ar-Throsis by using a 1.5-T MR scanner, with afast spin echo sequence: proton density-weighted, T2-weighted and fat suppression T2-weighted. They were evaluated on the size, incidence and localization of MR evidence of the joint effusion by images obtained in the closed mouth.
(1) To evaluate the size of the evidence of joint effusion, it was classified into the following five grades; nothing, a point, a line, a thick line and a band. The incidence of evidence of joint effusion in the upper joint space was significantly higher than that in the lower joint space. But there was no statistical difference in incidences of the evidence between the coronal and sagittal images.
(2) 353 TMJs (70.7%) in the upper joint space and 396 TMJs (79.4%) in the lower joint space were evaluated as the same grades on both coronal and sagittal images.
(3) 96 TMJ images (19.2%) in the upper joint space showed the evidence of joint effusion which was more than a thick line on the coronal and/or sagittal images. There were significant differences in the incidence of the evidence in sex and age. Therefore, the younger the subject's age the higher the incidence of the evidence.
(4) In comparison with the incidence and the size of the evidence of joint effusion on areas of the upper joint space, the evidence which was more than a thick line was most often seen in the anterolateral recess of the upper joint space.

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An autopsy study was performed on 174 mandibular condyles of 96 elderly Japanese. The size, shape, frequency and type of the change on articular surface of the condyles in elderly Japanese were investigated. The mean age was 72.0 years in 59 males and 83.8 years in 37 females. The mean age in females was significantly higher than in males. The mean antero-posterior diameter of the condyles was 11.2±1.21mm in males and 10.8±1.41mm in females. The mediolateral diameter was 22.0±2.28mm in males and 20.1±2.97mm in females. The differences between the sexes were statistically significant. Concerning the shape of the condyle, the most predominant was elliptical in superior view (55.2%), slightly rounded in posterior view (62.6%), and rounded in lateral view (73.6%). There were no sex differences of the occurrence. The changes of the articular surface, such as step, concavity, projection were observed in 66 out of 168 condyles (39.3%), excluding 6 condyles with advanced deformity. The incidence was 32 out of 105 (30.5%) in males and 34 out of 63 (54.0%) in females. The occurrence was significantly higher in females than in males. In conclusion, those specimens could be utilized as a standard for Japanese elderly persons.

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A multicenter randomized comparative study was conducted in 189 patients with temporomandibular joint arthrosis (TMJ) to find the optimal dose regimen for NK-433 (a new centrally acting muscle relaxant).
Patients were administered any one of doses of 50mg (50mg group), 100mg (100mg group), and 150mg (150mg group) of NK-433 for 2 weeks two times a day.
(1) Out of 189 patients enrolled, the Final Global Improvement Rates (FGIR) were analyzed in 51 patients of the 50mg group, 54 patients of the 100mg group and 50 patients of the 150mg group. The Overall Safety Rate (OSR) was studied in 58 patients of the 50mg group, 64 patients of the 100mg group and 58 patients of the 150mg group. And the Final Global Usefulness Rates (FGUR) were analyzed in 53 patients of the 50mg group, 60 patients of the 100mg group and 53 patients of the 150mg group.
(2) There was no siginificant difference among the 3 groups for “Moderate” and “Marked” improvement of FGIR, and the 150mg group was the highest rate with 74.0%.
(3) Complaints were seen in 37 patients, but none of them was severe.
(4) There was no siginificant difference among the 3 groups for “Usefulness” and “Very usefulness” of FGUR, and the 150mg group was the highest rate with 71.7%.
In conclusion, NK-433 was shown to be useful in the treatment of TMJ arthrosis, and an optimal dose of 150mg a day was suggested.

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Randomized comparative study by double blind experiment was conducted in 241 patients with temporomandibular joint arthrosis to determine the efficacy, safety and usefulness of NK-433 using 150mg of lanperisone hydrochloride (NK group) or of 7.5mg of lanperisone hydrochloride (CT group) for 2 weeks in twice a day continuously.
(1) Total number of patients enrolled was 241 (121 in NK group, 120 in CT group). Among those patients, 217 (108 in NK group, 109 in CT group) were adopted for the analysis of final global improvement, overall safety and usefulness.
(2) With respect to final global improvement, the effective rate (more than “moderately improved”) of NK group was 56.5% (61/108), and 39.4% (43/109) for CT group. NK group was significantly superior to CT group.
(3) With respect to overall safety, the safety rate (more than “probably safe”) of NK group was 92.6%, and 92.7% for CT group. No significant difference was observed between the two groups.
(4) With respect to usefulness, the rate of usefulness (“more than moderately useful”) was 55.6% (60/108) for NK group, and 38.5% (42/109) for CT group. NK group was significantly superior to CT group.
(5) As for “female”, “20's”, “initial”, “without other disease”, “masticatory muscle disorders” and “duration shorter than 1 year” in the characteristics of the patients for the changes of the global improvement, NK group was significantly superior to CT group.
(6) After 2 weeks, NK group was significantly superior to CT group.
In conclusion, NK-433 (150mg in twice a day for 2 weeks) is considered to be useful in the treatment of temporomandibular joint arthrosis.

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Nine patients with TMD (temporomandibular joint disorder), perimandibular ostitis and so on, associated with decreased marrow signal of the mandibular condyle on Ti-weighted MR images were presented. Their clinical diagnosis were perimandibular osteitis in 1 case, subcondylar fracture in 1 case, osteoarthrosis of TMJ in 7 cases. In one case, a complication of avascular necrosis at the femoral head was observed.
In the case of perimandibular osteitis, sequestrum of the condyle was seen on radiographs, and the corresponded areas showed low density on MR images. After 1.6 years the density of the area increased. In the case of subcondylar fracture, a low density area on MR images was seen in the center of the condyle. After 1.3 years, clinical symptoms were improved and the density of the area increased.
Most of the cases of osteoarthrosis with shorting and thin condyles on radiographs with decreased bone marrow signals progressed in 3 cases, disappeared in 1 case and was unchanged in 3 cases.
In the case with a complication of avascular necrosis at the femoral head, clinical symptoms were improved after 1.3 years, but the low density area of condyle had not changed.
Decreased marrow signals in T1-weighted MR images in temporomandibular joint seemed to be caused by various factors, such as the temporary avascular change by trauma or inflammation and atrophic condyle. It is speculated that these changes are associated with systematic or constitutional factors.
Most of these lesions seemed to be asymptomatic processes and substantial changes of the condyle were not necessarily associated with the clinical symptoms.

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