目的探讨成都地区青少年牙弓后段可利用间隙的增龄性变化，为临床应用全牙弓间隙分析提供依据。方法将1999-2000年在原华西医科大学口腔医院正畸科就诊的11-20岁初诊患者，按纳人和排除标准筛选，共获得526例，其中男232例，女294例。按领骨的矢状向、垂直向异常分类，通过头影测量分析获得牙弓后段可利用间隙量。分析成都地区青少年牙弓后段可利用间隙增龄性变化规律，用多变量相关分析检测牙弓后段间隙量与年龄、性别、安氏错抬类型、垂直骨面型的相关性。结果（1）下领牙弓后段间隙量与年龄、安氏错抬类型相关。（2）男女性的下领牙弓后段可利用间隙增龄性变化曲线有一定差异。（3）骨性U1类患者的牙弓后段可利用间隙增龄性变化量明显大于安氏IIU类患者。结论成都地区青少年的数值同国外数值差异较大，提示在进行全牙弓间隙分析时，应考虑种族的差异及错抬类型。

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.