Study on the influence of masticatory movement on the growth and development of the mandibular bone-Fusion of genetic and mechanical analyses-

目的研究了咀嚼对下颌骨生长的影响。因此，为了明确咀嚼对颌骨的影响，我们在研究1中研究了咀嚼对下颌骨形态和基因表达变化的影响，在研究2中比较了不同面部模式下各区域皮质骨的厚度和骨密度，以收集力学分析所需的基础数据。材料与方法研究1选用3周龄ICR小鼠，将实验组分为硬食组、软食组和软硬交替喂养组。实验开始后1周和4周，采用micro-CT测量下颌骨形态，进行h.e.染色，采用PCNA评价软骨细胞增殖能力。此外，采用激光显微解剖法观察基因表达的变化，并采用实时荧光定量PCR法评估与软骨生长有关的基因表达水平。研究2采用锥形束CT测量3种面部模式下皮质骨的厚度和密度。结果研究1：软性食物组与硬性食物组下颌骨形态有明显差异。组织学上，硬食物组髁突软骨增生性软骨细胞层明显增厚。硬食物组软骨细胞增殖能力最低。此外，在基因表达水平的变化方面，硬食物组与软骨细胞钙化和最终分化相关的基因表达明显更高。研究2:3种面部类型的骨皮质厚度和密度无明显差异。然而，面部型在所有区域的骨密度和皮质骨厚度均较低。讨论与结论我们的实验表明，咀嚼运动影响下颌髁软骨细胞的分化，对髁软骨生长和下颌骨形态有显著影响。此外，我们还认为咀嚼肌的特征可能会改变面部骨骼形态。少

PurposeIt 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 MethodsIn 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 … More 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.ResultsStudy 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 ConclusionOur 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