The purpose of the present study was to investigate the relationship between the occlusal change due to the exfoliation of primary teeth and TMD symptoms in primary school children, and to investigate the changes of TMD symptoms for three years in junior high school and high school adolescents. There were 105 subjects in primary school, 277 in junior high school, and 276 in high school.
The results obtained were as follows:
1. The children who were found to have TMD symptoms in the first year of observation, for 3rd- to 5th-school-year children in primary school, totaled 105. In 41.0% of them, the TMD symptoms continued in the second year of observation, for 4th- to 6th-school-year children, whereas 59.0% of the symptoms disappeared.
2. Children whose second primary molars exfoliated, and then the second permanent molars erupted, had disappearance of TMD symptoms.
3. As for the rate of continuing TMD symptoms for three years, it was higher in high school adolescents compared with junior high school students, especially in girls.
Three findings suggest that it is necessary to periodically examine the changes of TMD symptoms and occlusal changes of children and adolescents who are identified in school dental examinations.

View full abstract

A case of facial asymmetry with severe unilateral hypoplasia of the masticatory muscles is reported. A 45-year-old Japanese man was referred to our clinic on Dec. 18, 2002 with chief complaint of dull pain of the right masseter and molar teeth during chewing. He presented with left side facial hypoplasia which had been noted from an early age. The external ear was normal, the ears symmetrically placed and audition showed no abnormality. Maximal mouth opening was 58mm and the mandible did not deviate upon opening the mouth. Radiographic examination did not reveal any dental abnormalities but the left ramus and condyle of the mandible was found to be smaller than the right and to have a less well developed gonial angle. MR imagings of facial tissues showed that the masseter, temporalis and medial pterygoid muscles were grossly hypoplastic and the lateral pterigoid mildly so on the left side. The clinical findings thus suggested that this was not a typical case of a first and second branchial arch syndrome.

View full abstract

Two males, aged 15 years (patient 1) and 27 years (patient 2), presented with chief complaints of pain in the bilateral masseter muscles during jaw movement and because of trismus. Hyperplasia of the mandibular angles and bilateral swelling of the masseter muscles were noticeable. The interincisal mouth opening of patients 1 and 2 was 31mm and 22mm, respectively. Radiography and magnetic resonance imaging did not reveal any abnormalities other than hyperplasia of the coronoid process and the mandibular angles. Bilateral hypertrophy of the masseter muscles with chronic trismus associated with hyperplasia of the coronoid process and the mandibular angles was diagnosed, and surgical procedures were applied using an intra-oral approach. Since there was little improvement in the passive range of interincisal mouth opening under general anesthesia with muscle relaxation and even after resection of the bilateral coronoid processes, the bilateral masseter muscles were stripped and partially resected. Stripping of the bilateral pterygoideus medial muscles and bilateral mandibular anglectomy were necessary to achieve a good range of interincisal mouth opening. We think that their trismus might have been caused by the contracture and difficulty in extending the jaw closing muscles.

View full abstract

Condylar hyperplasia is known to be induced by previous trauma and hormone disturbance and so on, but the aetiology is far from elucidated. Here, we report a case of condylar hyperplasia accompanying malocclusion. In September 2000, a 60-year-old woman became aware of occlusal deviation after prosthetic treatment at a dental clinic. There were no signs of pain in the bilateral temporomandibular joints or trismus, but radiographic examination showed abnormality of the left condyle. Therefore, in July 2001 she was referred to our university hospital with chief complaint of malocclusion with the mandible deviated to the right. Clinical examinations revealed facial asymmetry and malocclusion to the mandible deviated to the right and clicking in the bilateral temporomandibular joints without pain or trismus. Radiographic, CT and MRI examination showed hypertrophy and lobulated change in the left condyle. We suspected benign tumor of the left condyle and she was treated with extirpation of the condylar tumor under general anesthesia. Pathohistological examination revealed fatty marrow and hypertrophy of the cancellous bone, therefore, the final diagnosis of the lesion was condylar hyperplasia. The facial asymmetry was improved and the patient was followed up for two years after the operation. The subsequent course was satisfactory and there were no signs of functional disorder or recurrence.

View full abstract

Murine brachymorphism (bm) has cartilage with glycosaminoglycans (GAGs) undersulfated. The phenotype is inherited as an autosomal recessive. Anterior transverse crossbite sometimes spontaneously occurs in BALB/c-bm/bm mouse (bm homozygotes) inbred. Temporomandibular joints of BALB/c-bm/bm mouse were histologically and biochemically evaluated.
We used BALB/c mice (control), BALB/c-bm/bm mice with normal occlusion (bm-Norm), and BALB/c-bm/bm mice with crossbite (bm-Mal). Coronal sections of control and bm-Norm groups aged 8 weeks were made and stained with hematoxylin-eosin, with the methods of alcian blue critical electrolyte concentration, and with sensitized high iron diamine methods after treatment of testicular hyaluronidase (bovine testis). After extracting condylar cartilage of control, bm-Norm, and bm-Mal groups aged 3 weeks and 13 weeks, sulfated GAGs were also measured using demethylmethylene blue assay.
Compared with the control group, condylar cartilage of the bm-Norm group was thinner and had an unclear zone of hypertrophic cells. Keratan sulfate and chondroitin sulfate were weakly stained in the bm-Norm group. The concentration of sulfated GAGs in cartilage of condyle in each group aged 13 weeks was lower than that in each group aged 3 weeks. The concentration of sulfated GAGs in cartilage of condyle in the bm-Norm and bm-Mal groups aged 3 weeks was lower than that in the control group. The concentration of sulfated GAGs in cartilage of condyle in the bm-Mal group aged 13 weeks was significantly lower than those in the control group and bm-Norm group. There was no significant difference between the concentration of sulfated GAGs in TMJ of mandibular shift sides and that in TMJ of non-shift sides of the bm-Mal group.

View full abstract

Aim: Recently, the lateral pterygoid muscle (LPt) has been investigated by anatomical studies. Although there have been some reports on morphometry by computer tomography (CT) imaging in medical imaging, there have been few reports on magnetic resonance imaging (MRI). The aim of this study was to measure the morphometry of human LPt noninvasively.
Method: Twenty-one subjects with normal dentition and without symptoms in temporomandibular joint were selected. We used Signa Horizon LX^® (1.5T, GE, USA) with fast gradient echo sequence (TR=9.6ms/TE=4.0ms) for this study. We measured the morphometry as follows: 1) the volume of both-side LPts, 2) the angle of LPt inferior head in axial slice, and 3) the anatomy of LPt in MRI with image analysis by Exavision lite^® (Zio, Tokyo) on a personal computer.
Results and conclusion: 1) The volume of right-side LPt was significantly larger than that of left-side LPt. 2) The run of both-side LPts was approximately orthogonal in the axial slice. 3) The LPt could be classified broadly into biceps and triceps, and the biceps accounted for about 80% of the total. From these results, it was suggested that MRI is useful for morphometry of LPt in humans.

View full abstract

A case of bilateral bony ankylosis of the temporomandibular joint caused by bilateral chronic parotitis is reported. A 52-year-old man was referred to our clinic by an otolaryngologist with the chief complaint of trismus. He had been treated with bilateral chronic parotitis by the otolaryngologist for twenty years. The maximum mouth opening range (MOR) was 4mm. Following diagnosis of bilateral bony ankylosis of the temporomandibular joint, bilateral condyloplasty was performed. After the operation, the maximum MOR increased to 23mm. The patient is now satisfied to be able to eat chunks of food. However, MOR had decreased due to aggravated chronic parotitis, so mouth opening execises were needed to increase MOR.

View full abstract