Two hundred and twenty-nine patients with persistent nonreducing anterior disk displacement of the TMJ, who visited our clinic between 1986 and 1991, were studied with respect to the symptoms and outcome of nonsurgical treatment.
The maximal interincisal distance (MID) before treatment ranged from 14mm to 62mm (mean: 33.2mm). 25.7% of the patients showed 40mm and more of the MID. 93.8% of the patients had arthralgia and/or myalgia, and 23.1% had myalgia only. There is thus a variety of symptoms of nonreducing anterior disk displacement. The longer the period of nonreducing displacement, the greater the resulting MID.
Nonsurgical treatment with an occlusal splint was performed for all patients, and 67% of them received occlusal treatments after the splint therapy. For 102 patients whose treatment was completed and for 5 patients under follow-up, the symptoms after treatment were compared with those before treatment (the treatment is on-going in 14 patients and has been suspended in 102 patients, and the result of treatment was unknown in 6 patients). The treatment duration ranged from 1 to 34 months (mean: 11.2 months). The patients who presented with arthralgia only at first visit had a shorter duration of treatment. The mean of MID before the treatment was 32.4mm, while that after the treatment improved to 45.1mm. The percentage of the patients who had arthralgia and/or myalgia before and after treatment was 96.3% and 25.2%. Compared with arthralgia, myalgia tends to remain, although the intensity reduced in the majority of the subjects.
Thus, TMJ pain and restricted mouth opening were significantly improved, indicating the effectiveness of the nonsurgical treatment in this study. These results show that anatomical reduction of displaced disk should be unnecessary to improve the symptoms. However, it is necessary to discuss a method to remove persistent myalgia in a large proportion of patients.

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The potential of ³¹P-MRS for the study of energy metabolism is widely demonstrated in animal models and human skeletal muscles. However there have been no studies reporting energy metabolism of human masticular muscle. This is beeause of the hard susceptibility in the head and neck region and the small volume of masticular muscle. The author devised a method for human masticular muscle especially masseter muscle energy metabolism by ³¹P-MRS and obtained a ³¹P-MRspectrum from human masseter muscle. The spectrum consisted of large phosphocreatine (Pcr) and ATP (γ, α, β) peaks, with a weak intraorganic phosphate (Pi) peak. After the exercise of clenching maximally for one minute Pcr decreased and Pi increased, but there was no change in tissue pH and ATP peaks. Pcr and Pi recovery occurred within 8 minutes of the end of the exercise.

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Sympathetic, sensory and motor innervation of the masticatory muscles was investigated in the rat by the horseradish peroxidase (HRP) method.
Experiments were performed using 24 Wistar rats. 40% HRP was injected into the masseteric, temporal, medial pterygoid, lateral pterygoid, anterior digastric and mylohyoid muscles. After a 24-hour survival period, the animals were perfused with fixative and the superior cervical (SCG), stellate (SG), trigeminal (TRG) ganglia and brain stem were dissected, sectioned and processed with tetramethyl benzidine method.
HRP injection into the masseteric, temporal, medial pterygoid, and lateral pterygoid muscles produced numerous labeled cells which localized at the central 1/2 of SCG, but only few cells in the anterior digastric and mylohyoid muscle cases.
Labeled cells were found ipsilaterally in the submandibular division in TRG. Their mean diameter in the upper muscles (24.3±4.9μm) was significantly smaller than those in the tooth pulp (27.8±5.5μm).
In the trigeminal motor nucleus, labeled cells after HRP injection into the masseteric muscles were localized in the dorsolateral part, temporal muscles in dorsal, medial pterygoid muscles in ventrolateral, lateral pterygoid muscles in ventromedial, anterior digastric muscles in dorsomedial and mylohyoid muscles in medial. The distribution pattern of neuron size of the masseteric muscles was bimodal, and that of the others unimodal. The mean diameter of labeled cells of the masseteric (26.0±4.3μm) and temporal muscles (26.1±4.3μm) was significantly larger than that of those in the medial pterygoid (24.5±3.3μm), lateral pterigoid (25.1±3.6μm), anterior digastric (24.9±3.3μm) and mylohyoid muscles (24.0±3.0μm).
Many labeled cells were found in the mesencephalic nucleus after HRP injection into the masseteric, temporal and medial pterygoid muscles, but no cells were found in the lateral pterygoid, anterior digastric and mylohyoid muscles.

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In this case, condyle hyperplasia has obvious chronic dislocation on the right side TMJ.
The male patient, aged 46, had few subjective symptoms related to TMJ affection and its dysfunction. According to his present history, it is inferred that the dislocated TMJ appeared around 30 years ago, when he was aware of his chin shifting to the left side. This case is characterized by mandiblar shift which progressed over a long period, slowly and without non symptoms 16 to 18 years of age.
A sliht limitation of lateral and anterior-posterior mandibular movement was recognized, but there were no oral functional disorders such as masticatory disturbunce or articulatory disorder. EMG data indicated that the action potential on the temporal muscle tended to increase more than the masseter muscle at the rest position. But it did not indicate a difference in size between the two muscles. Regarding the action potential on maximum biting, both muscles worked almost equally on the sound side of TMJ. On the dislocated side, although the action potential of the masticatory muscle was extremely low, Pat of the temporal muscle was hand high.
Based on the present symptoms, it appears that open operation is necessary for TMJ. reduction Currently, however, we are merely observing the progress because the patient has no complaint with his mandibular movement, though there is anxiety regarding a decline of function.

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A 38-years-old man visited our department complaining of slight swelling of the right temporomandibular joint (TMJ) and malocclusion. On examination, there was right TMJ noise at opening and closing the mouth, with open deviation to the right side and open bite of the right molar region, but trismus was not found.
Radiographic examinatien did not reveal resorption and deformity at the condyle and glenoid fossa. CT findings with double contrast arthrography and MR images showed that high density mass and low signal intensity mass occupied the right upper joint cavity, without right articular disk displacement. As the clinical diagnosis was a synovial chondromatosis, we performed synovectomy and removal of the particles by microscopic open-surgery. [under general anesthesia] Histopathological examination revealed a synovial chondoromatosis. The clinical result was excellent without recurrence of lesion and malocclusion over 2 years postoperation.

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Accurate diagnosis of temporomandibular disorders has become available by recent advances of magnetic resonance imaging and arthroscopic examinations. The present study was conducted to investigate craniofacial morphology in patients with internal derangement of the TMJ.
Subjects were selected from orthodontic patients with signs and symptoms of the TMJ who underwent MRI examination (GE-Signa 1.5 Tesla) before orthodontic treatment from August 1991 to November 1993. Thirty-four patients with internal derangement of stages III, IV and/or V, classified by Wilkes criteria, were used as subjects. The subjects consisted of 27 females and 7 males ranging in age from 12 to 42 years (an average age of 20.6 years). The subjects were divided into 2 groups: unilateral (right or left, 23 subjects) and bilateral (11 subjects). The amount of lateral shift of the Me point was measured in the unilateral group by use of posteroanterior (P-A) cephalogram. For the bilateral group, the mandibular plane angle to SN, ramus height and mandibular body length were analyzed on lateral cephalograms and compared with Japanese standards.
In the unilateral group, 21 (91%) of the 23 patients exhibited lateral shift of the Me point to the deranged side. In the bilateral group, steep mandibular plane, short ramus height and mandibular body length were revealed in comparison with the control.
From these findings, it is suggested that chronic internal derangements with degenerative joint disease may be relevant to lateral shift of the mandible, steep mandibular plane, short ramus height and mandibular plane, and that these morphological characteristics may become more severe, if internal derangement of the TMJ occurs before adolescence.

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The purpose of this study was to clarify the relationship between the coincidence of the right and left condylar translation and the length of horizontal condylar pathways in groups with temporomandibular (TM) joint dysfunction (TMD group) and TM joint normal function (normal group).
The length of horizontal condylar pathways of the TMD group was longer than that of the normal group in habitual opening movement. However, the comparison of the length of the right and left condylar translation pathways was not significantly different. The coincidence of the right and left condylar translation movement of the TMD group in the habitual opening movement had more variance than that of the normal group. In order to determine whether the length of horizontal condylar pathways relates to the coincidence of the right and left condylar translation, a linear correlation analysis was performed. The length of horizontal condylar pathways and variance of the right and left condylar translation in TMD group correlated significantly (p<0.01).
It was suggested that the TMD group had a variance in the right and left condylar translation movement and longer horizontal condylar pathways during habitual opening movement due to the loosening of TM joint structures.

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Perforation of the TMJ articalar disc (including posterior attachment) has been regarded as a kind of degenerative change in the TMJ resulting from anterior disc displacement and osseous abnormalities on the condyle. However, the clinical details remain to be elucidated.
The aim of this study was to clarify the relationship of perforation to the progress of TMJ arthrosis. 19 perforated cases and 84 non-perforated cases were identified by TMJ arthrotomography and analyzed by radiographic comparison.
The results were as follows:
Morphological analysis of the condyle and the articular disc reveals much more abnormality in the perforated than non-perforated cases. In particular, various kinds of disc deformity were found in every perforated case. Regarding the relationship of the articular disc to the condyle, 6% of nonperforated and non-perforated cases showed a normal relationship. The ratios of “with reduction” to “without reduction” for anterior displacement of the disc were not significantiy different for perforated and non-perforated cases. Morphological measurement of mandibular fossa revealed significantly smaller values in the horizontal diameter, vertical diameter and front length for perforated cases. In other words, perforated cases tended to have shallow and narrow mandibular fossa.
These results suggest that perforation of the TMJ articular disc is an advanced condition of TMJ arthrosis.

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One hundred fifty eight joints (79 patients) with temporomandibular disorders were studied with MRI and tomography in order to clarify the relationship between the bony changes of the condylar head and the displacement of the disk of the temporomandibular joint.
The bony changes of the condylar heads were seen in 77.8% of the joints with anterior disk displacement. All cases of erosion, osteophyte and deformity (3 cases, 9 cases, and 5 cases, respectively) had anterior disk displacement without reduction.
From these results, it is suggested that the bony changes of the condylar head are closely related to anterior disk displacement (p<0.001) and should be interpreted as signs of internal derangemet of the joint.

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In our department, we performed 288 arthroplasties on 236 TMJ ankylosis patients from 1934 to 1987. We investigated the inpatient and outpatient chart, the operation record, and the X-ray film for each patient in order to determine the etiology, onset age, and interpositional materials, as well as the prognosis, complication, sequela and so on. In this paper, we report and discuss the etiology and the onset age.
1. The number of operations has decreased since 1963. The reasons for this decrease may be the development of chemotherapy which reduces inflammation and also the fact that TMJ trauma is now found early due to advances in imaging techniques. Another reason may be the increase in the number of hospitals undertaking TMJ arthroplasty.
2. Inflammation was the most common cause (119 patients; 50.4%), followed by trauma (73 patients; 30.9%). Ten cases were regarded as congenital (4.2%). Recently the rate of trauma has been the predominant cause.
3. Concerning local inflammation, osteomyelitis was the most common (35 patients; 43.2%), followed by otitis media (32 patients; 39.5%), and parotiditis (9 patients; 11.1%).
4. Polyarthritis was most common (12 patients; 31.6%), followed by febrile disease (7 patients; 22.5%), and pneumonia (6 patients; 18.4%) as for systemic inflammation.
5. As for the types of trauna, fall was the most common (40 patients; 54.8%), followed by traffic accidents (20 patients; 27.4%). Forceps delivery was found in 6 patients (8.2%). Also two cases occurred after TMJ discetomy.
6. The age range of TMJ ankylosis patients was from congenital to 65 years old. The number of patients whose onset age was from 0 to 5 years old was the biggest (129 patients; 54.7%), followed by 6-10 years old (58 patients; 24.6%). Among all the TMJ ankylosis patients, 187 patients (79.2%) were under 10 years of age when injured.

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