Mandibular kinesiograph (MKG) type K5A-R (Myo-Tronics Research Inc.) can do an MKG recording for as long as 120 seconds.
However, obtained traces are volatile where photography is the only way to conserve the traces. We describe a way of recording MKG using a personal computer (PC). We also describe how we manufactured an interface unit and a program to utilize the K5A-R's merits. The PC used is one of the 8801 series (8-bit PC) (Nippon electric corp.). The interface consists of signal selector, level shifter, A/D converter and peripheral interface adapter ICs, where the output signals corresponding to the MKG trace from K5A-R are converted to 8-bit co-ordinates data and stored in the 32K memory by every 1/60 second interrupt in the A/D converted digitized form. The recording period was more than two minutes. The stored MKG data are saved in a disk file, reloaded into the memory, and utilized to display MKG traces of sagittal, frontal, vertical velocity and horizon tal planes on a CRT screen via our own BASIC and machine language program.
The method shown in this report makes it possible to take long MKG recordings, such as the lateral movement of the mandible, and to store them in disk files. It is also useful for explanation of dysfunctional state to the patient of temporomandibular joint dysfunction by demonstrating mandibular movement as a graphic image.

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To ascertain how pressure pain is modified by pain from cutaneous or subcutaneous tissue layers, pressure pain threshold (PPT) was measured in the temporomandibular joint (TMJ) with and without anesthesia using an iontophoretic device. One side of the TMJs was anesthetized by lidocaine and the other was delivered physical saline. PPTs were measured on both sides of the TMJs before and after anesthesia in the double blind manner. Pressure was applied with a steady pressure increment rate of 0.5kgf/s with the help of an originally developed PPT measuring system.
Normalized values of the PPT after iontophoresis were calculated based on those of before iontophoresis. The results showed 100.9±12.4 (mean±SD) and 105.3±27.3 in the saline side and lidocaine side, respectively. Since there was no statistical significance between the sides, it could be concluded that PPT in TMJ region is mainly induced by pain of TMJ components.

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A clinical study was carried out on 250 joints of 222 patients with temporomandibular disorders with special reference to the relationship between disk position and bony changes. The joints were classified into 5 types, according to the classification proposed by the Japanese Society of TMJ. The joints with type III and type IV disorders were subdivided into III ADR (anterior dis-placement with reduction), III ADNR (anterior displacement without reduction) and IV N (no displacement), IV ADR, IV ADNR, respectively, by the disk position. Disk displacement with/without reduction was observed in 76% of the joints. Type III ADNR showed the highest incidence. The incidence of bony changes were 34.5% in 87 joints with ADNR and 17.5% in 103 joints with ADR, whereas these changes were noted in only 3 joints exhibiting no disk displacement, indicating that the bony changes are associated with the severity of disk displacement. The female-male ratio was 1:2.3, and was higher in joints classified into type I and type IV ADNR. The mean age was 33.5 years, and was significantly higher in joints exhibiting bony changes in both ADR and ADNR groups. The mean period before visiting our clinic was 33 months, and was significantly longer in type IV ADR joints than type III ADR joints, and was shorter in type IV ADNR joints than type III ADNR joints. The chief complaint was pain in 58.4% of the joints studied. Pain was the chief complaint significantly more often in type IV ADNR joint than III ADNR joint. The maximum mouth opening was significantly smaller in ADNR joints than the other type of joints, but it was not related to bony changes. The treatment was effective in 60.3% of the joints, and was least effective in joints with bony changes.

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The most common direction of temporomandibular joint (TMJ) disc displacement is anterior. However, disc displacement also occurs in the pure lateral or pure medial direction, termed sideways disc displacement. There have been few systematic studies of the clinical and MRI findings of sideways disc displacement.
The purpose of this study was to evaluate the relations between the direction of disc displacement (medial disc displacement, lateral disc displacement, and anterior disc displacement) and clinical findings, including the duration of symptoms, joint pain, joint sound, and range of motion, as well as MRI findings, including disc shape, disc mobility, condylar translation and bone change of condyle. The study was based on MRI of 442 TMJs in 342 patients with clinical symptoms of TMJ disorders. The sagittal and coronal T1-weighted SE images (1.5 Tesla) were used.
MRI showed medial disc displacement in 19 joints (4.3%), lateral disc displacement in 20 joints (4.5%), and anterior disc displacement in 195 joints (44.1%). The incidence of joint pain, deformed disc, and bone change of condyle was lower in medial or lateral disc displacement than in anterior disc displacement. No statistical differences between lateral disc displacement and medial disc displacement was found regarding the clinical and MRI findings except for duration of symptoms. In conclusion, lateral or medial disc displacement may represent a different clinical entity from anterior disc displacement, but it remains unclear whether the clinical entity of medial disc displacement is different from that of lateral disc displacement or not.

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Our previous study demonstrated that the occlusal plane generally inclined superiorly toward the mandibular displaced side and that in G3 (19-53 year old group) only, the more the mandibular deviation, the more the incidence of TMJ disorders, This incidence was seen neither in G1 (10-14 year old group) nor in G2 (15-18 year old group).
The purpose of this study was to additionally examine the characteristics of the craniofacial morphology and the relationship between lateral displacement of the mandible and the symptom atic side.
The results obtained were as follows;
(1) In G2 and G3, the more the mandibular deviation, the bigger the difference of the ramus height (Cd-Go) between the mandibular displaced and the non-displaced sides, and the shorter the ramus height of the mandibular displaced side. Interestingly, this incidence was not seen in G1.
(2) The incidence of TMJ disorder symptoms was 39.0% at both sides, 28.0% at the TMJ of mandibular displaced side and 25.4% at the non-displaced side; while the rest (7.6%) could not clearly point out their symptomatic sides.

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An epidemiologic study of clinical signs and symptoms of temporomandibular disorders was conducted. 1978 students of two high schools were examined and analysed.
The prevalence of joint sounds, muscle and/or joint pain and difficulties in opening was 14.9%, 7.6% and 3.8% respectively. The prevalence of at least one symptom was 20.2%.
There were no significant difference in symptoms between the boys and girls.
The group with abnormal habits (deviated mastication, grinding and the clenching) had significantly higher prevalence of temporomandibular symptoms.
These traumatic factors are likely to be important as etiologic factors.
No significant difference was found between the malocclusion group and the control group.

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The histologic effect of trauma to the rat temporomandibular joint synovial membrane was investigated electron-microscopically. Trauma to TMJ was introduced by repeated condylar hypermobility. The results were as follows;
(1) Early reactions in the synovial membrane were A cell loss and fibrin deposits on the synovial surfaces.
(2) During its course the collagen fibers were exposed on the synovial surfaces.
(3) In the late stage (4-6 weeks after trauma), the fibrosis of synovial tissue stood out through the synovial surface and subsynovial tissue.

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We studied the efficacy of nonsurgical treatment in 206 patients (37 males and 169 females) with closed lock of the TMJ, who visited our clinic in 1994. All of the patients were diagnosed with the chart for primary diagnosis and treated with L type chart treatment. Nonsurgical treatment with L type chart was performed by mandibular manipulation technique, oral medication of anti-inflammatory drug, pivot splint therapy and manipulation assisted by pumping.
The results were as follows;
(1) 48 patients were unlocked by mandibular manipulation technique, 14 by medication, 12 by pivot splint therapy and 13 by pumping manipulation. Comparing the successfully unlocked group and the failure group, the locking duration and sound duration were significantly short, and the maximal mouth opening at the initial visit was small in the former group. On the other hand, the degree of pain at the initial visit, was significantly bigger in the unlocked group than in the failure group.
(2) Thirty (18.7%) patients who had closed lock suffered from relapse.
(3) Forty seven (74.6%) patients who had closed lock within 2 weeks were unlocked, however 17 (16.8%) patients who had closed lock more than 1 month were unlocked.
(4) One hundred sixty-three (79.1%) patients who received nonsurgical treatment improved in spite of discrepositioning. Locking duration in the effective group with nonsurgical treatment was significantly smaller than in the ineffective group.

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In our department, we performed 288 arthroplasties on 236 TMJ ankylosis patients from 1934 to 1987. We investigated 37 cases with cephalometry whose onset age was from 0 to 15 and whose first operations were performed at the First Department of Oral and Maxillofacial Surgery, Tokyo Medical and Dental University. The results were as follows;
(1) Mandibular deformities of the patients with the TMJ ankylosis due to inflammation were more serious than those of the patients with the TMJ ankylosis due to trauma.
(2) Mandibular development was restricted in the patients with limited preoperative mouth opening.
(3) In the patients who had the most restricted mouth opening preoperatively, SNB and Ramus inclination were inclined to shift into the minus SD region, and the Gonial angle, Mandibular plane, and Y-axis were inclined to shift into the plus SD region.
(4) In five cases who had undergone arthroplasty before the growth spurt, facial growth improved.

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