| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2006: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2005: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
Purpose
It has been reported that mandibular bone growth is greatly influenced by mastication. Therefore, to clarify the influence of mastication on the jaw bone, its influence on changes in mandibular bone morphology and gene expression was investigated in study 1, and the thickness and bone density of the cortical bone in each area were compared among different facial patterns in study 2 to collect basic data necessary for mechanical analysis.
Materials and Methods
In study 1, using 3-week-old ICR mice, the experimental groups comprised a group in which hard food was fed, that in which soft food was fed, and that in which hard and soft foods were alternately fed. One and 4 weeks after initiating experiments, mandibular bone morphology was measured using micro-CT, H. E. staining was performed, and the proliferation ability of chondrocytes was evaluated using PCNA. Furthermore, changes in gene expression were observed using the laser microdissection method, and the quantitative level of g
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ene expression regarding cartilaginous growth was evaluated using the real-time PCR method. In study 2, the thickness and density of the cortical bone in 3 types of facial patterns were measured using cone-beam CT.
Results
Study 1 :
A marked difference in mandibular bone morphology was noted between the soft and hard food groups. Histologically, the hypertrophic chondrocyte layers in the mandibular condylar cartilage were significantly thicker in the hard food group. The proliferation ability of chondrocytes was lowest in the hard food group. Furthermore, regarding changes in the level of gene expression, the expression of genes related to the calcification and final differentiation of chondrocytes was significantly higher in the hard food group.
Study 2 :
No significant differences in the thickness and density of the cortical bone were detected among the 3 types of facial patterns. However, the dolico facial type showed low values for the bone density and thickness of the cortical bone in all areas.
Discussion and Conclusion
Our experiments revealed that masticatory movement influenced the differentiation of the mandibular condylar chondrocytes, suggesting a marked influence on condylar cartilaginous growth and mandibular bone morphology. Furthermore, it was also suggested that the characteristics of the masticatory muscles may change facial skeletal morphology. Less
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