The fragile X mental retardation (FMR) syndrome is the largest source of inherited mental retardation. The syndrome is usually caused by the transcriptional silencing of fragile X mental retardation gene (FMR-1). An 18 years old male wascompla띠ing of multiple toαh missing and abnormal facial profùe, of which signs were matemally dominant in his family. In the C)π。gene디c analysis the pa디ent and his parents did not show any discontinuity in the long arm end of X chromosome, but in the PCR produαs targeω19 the CGG repeat sequence in the 5' untranslated region of FMR gene both the patient'’ s and his mother' s gDNAs produced a normal and an extra bands, sized about 400 and 800 bps, respectively, while the his father' s gDNA produced only one normal band, sized about 400 bps. 까1US ， we suppose that the pa디.ent has heterozygotic alleles of FMR gene inherited matemally, and that the patient s FMR gene was in a premutated state relevant to the dentofacial abnormalities.

The temporomandibular joint (TMJ) showed characteristic anatomy and functions contrast to the other joints. In particular, children or young adolescent with the progressive temporomandibular disorder (TMD) showed remarkable changes in their mandibular growth and occlusion. The purpose of this study was to elucidate the functional and biomechanical causes for the maxillofacial deformities of TMD. A typocranial experiment was performed using a plastic skull model by simulating the mandibular movement after condylectomy. The directional forces of masticatory and suprahyoid muscles were reproduced on the typocranial skull model by elastics connecting between mandible and adjacent bony structures. Resultantly, the mandible of unilaterally or bilaterally condylectomized mandible was rotated downward and backward by the activation of masticatory and suprahyoid muscles. When unilaterally or bilaterally condylectomized mandible was activated by masticatory, suprahyoid and perioral muscles, the mandible was less rotated downward and backward than the cases activated by masticatory and suprahyoid muscles only. In the typocranial experiment after unilateral condylectomy the mandible was rapidly deviated toward the affected side, but this deviation was much reduced when the mandible was intensely supported by perioral muscles. By the compensatory response against the overload of TMJ due to the mandible body resection the typocranial experiment also produced the deepening of antegonial notch by the increased force of mylohyoid and perioral muscles. These findings suggest that after condylectomy the posterior fibers of mylohyoid and perioral muscles become hypertrophic and induce the characteristic mandibular deformities, i.e., deepening of antegonial notch and bowing of posterior ramus, which are similar to the mandibular changes in the progressive TMD.

Osteoarthrosis in TMJ is known to accompany characteristic features of the craniofacial malformation and malocclusion. In order to explain the mechanism that brings about the typical mandibular changes relating to the frequent clinical symptom, i.e., the limited mouth opening in TMJ patients. The present study investigated the mandibular morphology of the rabbit, also intentional TMJ osteoarthrosis was performed on the TMJ of the rabbits and their morphological changes were observed. A total of 12 New Zealand house rabbits weighing an average of 3 kgwere used and all left side joints were surgically meniscectomized and right side joints were used as controls. The rabbits were sacrificed in one week, two weeks, one month, three months and 5 months after the menisectomy, and the removed TMJs were examined by histological and radiographical methods and analyzed statistically. It was found that the mandibular morphology caused by osteoarthritis in the TMJ was characterized by the decrease in size of the ascending ramus, posterior ramus bowing, deep antegonial notch and thickening of the cortex in inferior and posterior borders of the mandible, that the similar features were also observed in the rabbit mandible. When the menisectomy was performed in the unilateral side of rabbit TMJ, the mandibular changes including the increased depth of antegonial notch and posterior ramus bowing occurred only on the affected side. These data suggested that the limitation of the mandibular movement and altered masticatory pattern by meniscectomy affects the structural remodeling of the mandible and TMJ likely the TMJ osteoarthrosis