The purpose of the present study was to survey the incidence of the TMD in children and adolescents. A total of 5, 996 (3, 281 males and 2, 715 females) from pre-school to high school was examined in this study.
The subjects were divided into five groups according to class, such as pre-school (PS), junior class of primary school (JPS), senior class of primary school (SPS), junior high school (JHS), and high school (HS).
The results were as follows:
1. The number and incidence of TMD were 1, 145 (17.1%) out of 5, 996. In each group, PS, JPS, SPS, JHS and HS were 18 (5.1%), 74 (7.9%), 153 (14.6%), 291 (20.8%), and 609 (26.9%), respectively. The incidence of TMD significantly increased with age.
2. There were no differences based on gender from PS to JHS, but females showed a higher incidence significantly than males in HS.
3. TMJ sounds were found to be the most frequent among the TMD symptoms.

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A case of anterior displacement that occurred after amputation of the bilateral coronoid processes is presented. A 27-year-old woman visited our department complaining of severe limitation of mouth opening. Plane radiography, panoramic radiograph, and three-dimensional computed tomography revealed bilateral hyperplasia of the coronoid processes. Amputation of the bilateral coronoid processes was performed by an intraoral approach under general anesthesia. This operation immediately resulted in an increased interincisal opening, but it caused anterior displacement of the mandible. Following jaw-stretching exercises with a splint, it was improved at two months postoperatively. A year after the operation, the patient's vertical opening is 40mm, and there has been no sign of anterior displacement of the mandible.

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To reduce the disc in patients with anterior disc displacement without reduction, occlusal splint threrapies have been used in the treatment after pumping-manipulation procedures as usual. However, there is not enough evidence to show whether such occlusal splint therapies influence the prognosis of patients treated with pumping-manipulation. This study aimed to examine the effects of two kinds of occlusal splint therapies: anterior repositioning splint therapy (ARS), and stabilization splint therapy (SS), after pumping-manipulation procedures.
Forty-three patients: 36 females and 7 males, with a clinical diagnosis of unilateral anterior disc displacement without reduction, were studied. The mean age was 37.9 years (range, 17 to 78 years). Twenty-four patients underwent pumping-manipulation procedures followed by occlusal splint therapies. The remaining 19 patients were not treated with an occlusal splint after pumping-manipulation procedures, as control subjects. All of the patients were followed up for one month.
As a result, occlusal splint therapies with ARS for 16 patients whose disc unlocked clinically after pumping-manipulation procedures, were significantly effective for preventing re-closed lock, as compared with control subjects (p<0.01). However, occlusal splint therapies with SS were not beneficial to management of joint pain and other symptoms in 8 patients whose discs were not successfully unlocked by pumping-manipulation procedures.

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It has been accepted that splint therapy for repositioning the condyle and disk, and subsequent occlusal reconstruction, are effective for treatment of patients with reducible anterior disk displacement. In this article, two orthodontic treatment cases of deep bite with temporomandibular joint (TMJ) disorders are presented, to examine the availability of such a therapeutic system. The first case is a 34-year-old female patient with deep bite. Her problems were lingual axiversion of the upper central incisors, right TMJ pain, and disturbance of mouse opening. After repositioning the condyle and disk by use of an anterior repositioning splint, orthodontic treatment was performed for 22 months. After the treatment, all the TMJ symptoms were eliminated, with a substantial correction of the occlusion. Repositioning of the anterior disk displacement in the right TMJ was also achieved. The second case is a 14-year-old female patient. Her main problem was malocclusion at the anterior region, right TMJ pain, and disturbance of mouse opening. An anterior repositioning splint was used for condyle and disk repositioning, and then orthodontic treatment was carried out for 29 months. After the treatment, all the TMJ symptoms were improved, although repositioning of the right TMJ disk had not been achieved.

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To clarify the correlation between occlusal force and intra-articular pressure of the temporomandibular joint, we simultaneously measured occlusal force and intra-articular pressure in the upper joint space.
Four patients (4 joints) with closed lock of the temporomandibular joint, and 4 volunteers (4 joints) without temporomandibular disorders, were selected for this study. A prescale 50 H type R, and a transducer for monitoring arterial blood pressure, were used to measure occlusal force and intra-articular pressure, respectively.
The correlation coefficient between occlusal force and intra-articular pressure ranged from 0.710 to 0.954, and the coefficient of determination ranged from 0.504 to 0.910. These results show that intra-articular pressure is in direct proportion to occlusal force. The regression coefficient of the subjects ranged widely (15.3∼270.9).
These results indicate that an increase of occlusal pressure is one factor for weighting of overload in the temporomandibular joint.

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Pumping manipulation is not only effective treatment for temporomandibular joint (TMJ) closed lock, it is also a safe treatment, because of few complications. This report describes an unusual case of progressive irreversible change in occlusion following pumping manipulation in combination with intra-articular injection of sodium hyalulonate in other hospital 11 months ago. A 55-year-old woman was referred to our department because of pain in the right TMJ and difficulty in chewing. The patient had painful limited mouth opening (34mm), tenderness of the right TMJ and masseter, and open bite except right second molar. MRI of the right TMJ showed anterior disc displacement without reduction with bone change, inferior displacement of the mandibular condyle, and high signal intensity of thickening posterior disc attachment on T2-weighted image. The lesion was diagnosed as osteoarthritis and open bite induced by inflammation of the posterior disc attachment of the TMJ. Injection of steroid into the posterior disc attachment was performed, followed by splint therapy and medication. Pain and range of motion improved, but open bite and difficulty in chewing were unchanged and were treated with prosthodontic occlusal reconstruction. The patient's post-treatment course was satisfactory without recurrence of symptoms. Post-treatment MRI and MPR-CT showed the condyle position to have been relatively improved by boneformation from the glenoid fossa side, and inflammation of the posterior disc attachment had disappeared.

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Adult rabbits (Japanese white rabbits) had their mouths held forcibly open a distance of 30mm for three hours, once and the course of adhesion in their temporomandibular joints was examined as a function of time over 60 days after the treatment under a light microscope and a confocal laser scanning microscope. The results were as follows:
1. Adhesion formation was observed in 10 out of 15 rabbits, 17 out of the 30 joints.
2. Five out of the 10 rabbits had adhesion formed in the upper joint compartment, while five had adhesion in the lower joint compartment.
3. Adhesions in the upper joint compartment were often more extensive than those in the lower joint compartment.
4. Adhesive tissues changed over time into a collection of tissues containing many fibrous connective tissues.
These results suggest that one day's forced mouth-opening stress is enough to induce adhesion formation in the joint compartment, and this experimental model will be useful in future studies of fibrous adhesion.

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The aim of the study was to assess the capability of hypocycloidal tomography and Orthocubic super-high-resolution CT (Ortho-CT) comparing osseous structures' change in many sections (lateral part, central part, medial part) of the temporomandibular joint (TMJ).
This method was applied to 60 TMJs of 30 TMJ disorder patients. The subjects were 4 males and 26 females (mean age, 30.8 years). We used hypocycloidal tomography, which corresponds to the center of the condyle, and this part image was made into the center of the fossa and the condyle. The 2nd section of the lateral was made into the lateral tomogram from there, and the 2nd section of the medial side was made into the medial side tomogram. We selected an Ortho-CT image identical to three levels of tomogram and compared their Ortho-CT 180 images. Examination method was classified as mandibular fossa and condyle head, and it was classified into osseous abnormalities and normal bone structure. Ortho-CT has a high degree of concordance with tomography, and as for osseous abnormalities, Ortho-CT was observed rather than the hypocycloidal tomography in all tomographic part.
These results suggest that Ortho-CT is more sensitive for osseous abnormalities than conventional tomography, and therefore seems to be a better alternative to conventional tomography to evaluate osseous abnormalities of the TMJ.

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A case of severe bony ankylosis of the temporomandibular joint, which caused micrognathia, is reported. A 43-year-old man was referred to our clinic with the main problem of trismus. He had jaw movement limitation due to TMJ ankylosis, resulting from the fracture of bilateral condylar processes in his childhood. The maximum mouth opening was 11mm, and X-ray examination revealed deformity of the bilateral mandibular heads and severe bony ankylosis on the left mandibular head. We performed an osteoarthrotomy and inserted a free skin flap to the resected area on the left side. On the right side, a condylectomy was performed. After the operation, the maximum mouth opening increased to 30mm, but micrognathia remained. Therefore, we conducted genioplasty and an iliac bone graft, at 11 months after the initial operation. Since these operations, the patient has been satisfied with the result of improvement of mouth opening disturbance and facial appearance.

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Recently, magnetic resonance (MR) imaging in the Temporomandibular Joint (TMJ) has been reported to be useful. However, sometimes it is difficult to get fine MR images because the TMJ is very small and anatomically contains many kind of tissues. The purpose of this study was to compare a high-resolution 4 cm coil, which is being preliminarily manufactured to this study, with a TMJ coil, in phantom and clinical studies.
The following results were obtained:
1. In the phantom studies, the signal-to-noise ratio (SNR) of the 4 cm coil was larger than that of the TMJ coil, from the surface to 4.2 cm.
2. In clinical studies, the 4 cm coil was equal to the TMJ coil in description of the disk form, and the 4 cm coil was superior to the TMJ coil in descriptions of the retrodiscal tissue and the lateral pterygoid muscle.
These results suggested that the 4 cm coil was useful for MR imaging in the TMJ.

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It is consistent that lavage manipulation is applicable for closed lock cases in internal temporomandibular joint derangement. The clinical purpose of this technique is drainage of viscous synovial fluid, stripping of micro-fibroadhesion, and washing out residual chemical mediators in the upper joint space. In this study, 17 patients who suffered from limited mouth opening and severe pain associated with a closed lock situation, received lavage manipulation, under sedation, and the clinical outcome was satisfactory. Additionally, application of sedation that contributed to facilitation of operative procedure and pain control during manipulation, was found to have clinical significance.

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We report a case of posterior open bite by a thickness of retrodiscal tissue.
A-27-year-old woman, who complained of difficulty in closing her mouth, visited our hospital on November 18, 2000. There was a tenderness and mobility pain in the left temporomandibular joint (TMJ). It is not limiting mouth opening, about 40mm with a pain of affected side, then posterior open bite.
In MR imaging, there was thickness of the retrodiscal tissue of the left TMJ. Lavarge including TMJ scopic examination doesn't come into effect on. Then arthroscopic surgery and extraction of the bilateral mandibular third molar tooth was performed, on December 15, 2000.
As a result, her complaints improved after the surgery, and kept good condition.

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