The patient was a 27-years-old woman who had be performed with Alveolar segmental osteotomy and bilateral sagital splitting ramus osteotomy for left TMJ symptom of pain and clicking. Although left TMJ symptom of pain resolved, but developed intermittent locking, right TMJ pain and mandibular deformity after surgery. For this reason, she visited our department.
Panoramic radiograph and Frontal cephalogram showed enlarge left of mandible surrounded mii-plate and did not reveal resorption or deformity at bilateral condyle. MR images showed deformity of right articular disk and anterior disk displacement of left TMJ. The patient underwent intraoral vertical ramus osteotomy under general anesthesia. We followed up for 8 months after operation, TMJ symptom resolved and mandibular deformity was improved.

View full abstract

In order to investigate the relationship between dental attrition and temporomandibular joint (TMJ), 532 Jilin rural people in China, who had severe dental attrition, were examined about the dental condition and TMJ symptoms.
1) Individual mean decayed, missing and filling teeth were 0.5, 0.2 and 0.1 teeth, respectively, and malocclusion was found in 12 people (2.3%) and not in 520 people (97.7%) of the total sample.
2) The incidence of dental attrition was found in 99.6% (low grade: 45.7%, severe grade: 53.9%) of the total sample and was in creased with aging, but was not correlate dwith sex.
3) TMJ dysfunction was found in 26 people (4.9%) by clinical examination and not in 506 people (95.1%) of the total sample. There were no patients who have TMJ pain. Painless TMJ sound was found in 25 people (4.7%) and was increased with aging. TMJ sound was more found in those who have severe attrition (7.0%) than slight attrition (2.0%).
Thus, dental attrition, harmonized with individual environment, should be considered as a physiological adaptation to keep the good relationship between occlusion and TMJ in the masticatory system. In other words, dental attrition with aging might not induce a TMJ disorders.

View full abstract

The purpose of this study is to find the factors related to the adaptability of newly asessed protrusive occlusion initiated with the repositioning appliance. Twenty six TMD patients (14 female and 12 males; mean age of 30.3±8.6y) with disc displacement having difficulty and/or pain on opening were divided into two groups based on the adaptability of the repositioning appliance. The adaptive group (group A) and the non-adaptive group (group N) were examined in terms of age, gender, MR findings, range of jaw opening, anterior overbite, and over jet. All the patients examined in this study were followed up for at least two years after repositioning appliance therapy. Ten of the patients were categorized in group A, and 16 were in group N. It was discovered that after wearing the repositioning appliance over a week, the patients in group N experienced discomfort in TMJ or masticatory muscles. Although over jet in group A (5.3±3.1mm) showed a significantly bigger overlap (p<0.05; t-test) than group N (2.7±1.4mm), the rest parameters didn't. Horizontal overlap in anterior teeth could be one of the intrinsic factors affecting adaptability of anterior therapeutic position.

View full abstract

Mouth opening training has been performed as a part of the physical therapy for the treatment of mandibular movement disorder. The mouth opening exercisers used in the therapy are based on a simple mechanism that increases intermaxillary and mouth opening distances.
We have been in charge of research and development for a mouth opening/closing training robot based on the mechanism of a mastication robot that allows computer-controlled reproduction of physiological mandibular movement (Waseda Jaw, 1986-).
This paper outlines the development of the 4th mouth opening/closing robot, Waseda Yamanashi-4 (WY-4). This computer-controlled robot provides 3 degrees of freedom for mandibular movement, that is, opening/closing movement, anteroposterior movement, and lateral movement. The robot has benn developed to compensate for lost function in patients with mandibular movement disorder and to provide them with natural mandibular movement. At the same time, the robot aims at introducing and spreading medical robotics in the dental field. Particularly, it aims at establishing dental robotics. The system has been used for patients with articular mouth opening disturbance by temporomandibular joint disease as well as for those with cicatricial mouth opening disturbance by maxillofacial injuly. The system has been effective for the physical therapy in the treatment of mandibular movement disorder.

View full abstract

The present study was carried out to investigate histologically and histometrically the effect of basic fibroblast growth factor (bFGF) on the growth of the rat mandibular condyle in organ culture. The mandibular ondyles were removed from rats immediately after birth, and then cultured for 1 to 8 days in 2 kinds of media, namely serumless BGJb (Group 1) and serumless BGJb with bFGF 100ng/ml (Group 2). Histologically, the mesenchymal cells in the layer of proliferation in Group 2 at 6 and 8 days showed a marked increase in cell number compared with those in Group 1. Histometrically, the size of the mandibular condyles and the thickness of the layers of articular surface and proliferation in Group 2 at 8 days were significantly greater than those in Group 1, suggesting that bFGF had stimulated the proliferation of mesenchymal cell which had resulted in an increase of the number of chondrocytes in the layers of differentiation and hypertrophy there by leading to the enlargement of the condylar size.

View full abstract

We had an orthodontic case with condylar resorption that was stopped by improving the malocclusion. The patient was a 19 year old female with complaints of high canine and left TMJ sound. Her occlusion was unstable since it was only supported by the molars. We diagnosed her Angle class II malocclusion with mandibular backward rotation and TMJ osteoarthrosis from X-ray data. We corrected the occlusion by including the creation of anterior teeth centric stops and anterior guidance to decrease the overload of TMJs. During the initial observation, bilateral condylar resorption was observed, but while stabilizing the occlusion, her condylar resorption ceased. The result has been good for 7 and a half years. This case suggests that occlusal stability is an important factor in recovery of TMJ condition.

View full abstract

The aim of this study was to investigate the usefullness of Ortho-CT for the diagnosis of intracapsular fracture in the mandibular condyle.
Ortho-CT system can obtain multisectional images by only one exposure. It is assembled on a Scanora and uses a 4 inch image intensifier and small conical beam with an exposure field of 3 cm×3.5cm. Images in three sectional planes can be reconstructed from the data by one exposure in approximately ten minutes. Each voxel is an orthocubic figure whose size are 0.133mm, and the imaging area is consisted of 240×280×280 voxels. Since the exposure field is small, the patient dose is very low compared with ordinary CT examination.
Tow cases of intracapsular fracture of the mandibular condyle were diagnosed with rotational panoramic radiography, lateral oblique transcranial projection and Ortho-CT. In case 1 intracapsular fracture of the mandibular condyle was cofirmed by Orhto-CT but rotational panoramic radiography and lateral oblique transcranial projection could not be useful for the detection of the fracture. In case 2 small free bone fragment by the fracture was defined clearly by Ortho-CT but rotational panoramic radiography and lateral oblique transcranial projection could not be useful.
In conculusion this study suggests that Ortho-CT is superior to rotational panoramic radiography and lateral oblique transcranial projection for the examination of the intracapsular fracture of the mandibular condyle.

View full abstract

The purpose of this study was to clarify the characteristic of bite force distribution on the dental arch in the TMD patients and to evaluate a efficacy of diagnostic test for TMD based on the bite force distribution. Bite force was measured during maximum voluntary clenching at intercuspal position by pressure sensitive film, “Dental Prescale 50H, type R (Fuji photo film, Co.). Subjects involved in this study were 64 TMD patients and 42 normal subjects.
Asymmetry index of bite force (AI) was defined as a percentage of the difference in bite force between the left and right sides to the sum. AI was 14.5±12.6% in TMD patients and was 9.3±6.3% in normal subjects. Significant difference was not observed in between these two groups (p=0.06). The number of subjects whose AI were out of 2 S. D. range was significantly larger in TMD than in normal subjects (p<0.01). The number of subjects in whom the proportion of the bite force on the first molar to the total bite force was lower than mean -2 S. D. was significantly larger in TMD patients than in normal subjects (p<0.01). A diagnostic test for TMD using these two criteria showed low sensitivity (37.5%) and high specificity (96.4%). If other parameters would be added, this test would become useful clinically.

View full abstract