Objective: Using type X collagen as a marker, this research was designed to examine the alteration of condylar growth in response to mandibular condylar forward positioning. Methods: One hundred female Sprague-Dawley rats with 5 weeks of age were randomly divided into five experimental and five control groups. In the experimental groups, bite jumping appliances created forward positioning of the condyle. The experimental rats, together with the age-matched controls, were sacrificed on days 3, 7, 14, 21 and 30, respectively. Tissue sections were cut in the sagittal plane through the mandibular condyle and were processed for in situ hybridization and immunostaining of type X collagen and then for quantitative imaging analyses. Results: (1) Both type X collagen mRNA in situ hybridization signals and type X collagen immunostaining were localized within the hypertrophic zone of the condylar cartilage. (2) With condylar forward positioning, the level of type X collagen mRNA signals (8541±74 μm2 at peak) was 300% higher than that in the controls (2117±78 μm2 at peak); type X collagen immunostaining in condylar advancing groups (54864±134 μm2 at peak) was 254% more than that in the controls (15470±121 μm2 at peak). (3) The amount of type X collagen mRNA signals and immunostaining in experimental and control groups reached the highest levels at day 14 and day 21, respectively, indicating that an increase in endochondral ossification occurred 21 days after condylar forward deviation. Conclusion: Condylar forward repositioning provokes an enhanced maturation of condylar chondrocytes resulting in increased synthesis of type X collagen, a extracellular protein that attributes to endochondral ossification.

This study was to examine the effects of mechanical stimuli alone and coupled with some inhibitors of related signaling pathways on early cellular responses. MG-63 cells were subjected to cyclic uniaxial compressive or tensile strain at 4000 lstrain, produced by fourpoint bending system. The effects of mechanical strains alone and coupled with inhibitors of microfilament and receptor tyrosine kinase (RTK) on activation of extracellular signal-regulated kinase (ERK), c-fos mRNA, and c-Fos protein were examined. ERK could be activated by mechanical stimuli in 5 min and so could be c-fos mRNA and c-Fos protein in 30 min. Tensile stress had a more obvious effect than compressive one. Early ellular responses were connected with cytoskeleton and RTK pathways during the transduction of mechanical signals. The property of strains was an influential factor for the activation effects.

目的：定量分析大鼠下颌持续前伸对颞下颌关节窝新骨形成的影响。方法：模拟临床固定功能矫治器，引导大鼠下颌前伸，制取下颌骨和颞下颌关节组织切片，采用LeicaQ550IW计算机辅助图像分析系统进行定量分析。结果：大鼠在下颌持续性前伸条件下，其颞下颌关节窝后份有明显的新骨沉积。第3天时，实验组和对照组间新骨沉积无明显差异，从第7天开始实验组与对照组有明显区别，在第21天时达到高峰，接近30天，二者间的差别趋小。结论：前伸大鼠下颌后，颞下颌关节窝有新骨形成，并可采用计算机辅助图像处理系统进行定量分析。

目的从生物力学角度分析前伸下颌的作用机理，为临床应用提供理论依据。方法采用数值应力分析法，首次建立了相似性好的“下颌骨矫形系统”的三维正交各向异性有限元模型，对前伸下颌时髁突的受力进行研究。结果髁突软骨表面的前部出现压应力集中区（-2425g/cm2～-7399g/cm2），后上部出现张力区（10000g/cm2），髁突发生顺时针向位移。结论生物力学分析表明，前伸下颌能促进下颌髁突的生长，有利于骨性Ⅱ类错的治疗。

目的：研究不同重建情况下相关口颌肌肉和韧带的约束反力变化规律，为Herbst矫治器临床应用提供相关依据。方法：在已建立的下颌骨硬组织三维有限元模型基础上附加Herbst矫治器，建立颞下颌关节一下颌骨-Herbst矫治器系统的三维正交各式各样向同性有限元模型，根据临床和相关文献设计重建的类型，通过计算机相关口颌肌肉和韧带的约束反力。结果：不同重奸时嚼肌浅层（SM）、翼内肌（MP）、颞下颌韧带浅层（STL）、颞下韧带深层（DTL）、翼外肌下头（ILP）、翼外肌上头（SLP）所受的力始终为零；颞肌中束（MT）、颞肌后束（PT）、茎突下颌韧带（StL）、蝶下颌韧带（SpL）受力随着下颌水平前伸距离的增大、垂直向移位距离的减少而增长率大；颞肌前束（AT）和嚼肌深层（DM）随着下颌水平前仲距离的增大、垂直向移位距离的减少而减小。相关口颌肌肉所受终束反力的数值相差最大的为茎突下颌韧带，其次为蝶下颌韧带和颞肌后束，再次为颞肌前束，其余相差不大。约束反力最大值为32.48kg，最小值为0kg，力值在可承受范围之内。结论：茎突下颌韧带、蝶下颌韧带、颞肌后束和颞肌前束在Herbst所引起的下颌骨功能改建中，起了相当重要的作用。本文设计的5组重建类型（下颌水平前伸3～7mm，垂直打开4～2mm）均在临床选择之列，最佳组合根据患者的适应能力及畸形情况进行选择。