双侧第二磨牙正锁[牙合]对下颌骨发育和位置的影响

The effect of bilateral scissor bite of second molars on the growth and position of mandible

目的研究双侧第二磨牙正锁[牙合]对下颌骨发育和位置的影响，为正确诊断、制定正畸方案和临床治疗提供参考。方法选取20例双侧第二磨牙正锁[牙合]安氏Ⅱ类1分类高角成年女性作为实验组，30例无第二磨牙正锁[牙合]安氏Ⅱ类1分类高角成年女性作为对照组，最大牙尖交错位时拍摄头颅侧位片，采用Jarabak分析法和模型测量法测量并进行统计学分析。结果与对照组相比，第二磨牙正锁[牙合]患者下颌体长度、下颌第二磨牙处基骨弓宽度、∠N-S-Ar和∠Ar-Go-N均减小（P〈0．05），S-N／Go-Me和∠S-Ar-Go增大（P〈O．05），而下颌升支高度、下颌第一前磨牙、第一磨牙基骨弓宽度、S-Ar／At-Go、∠N-Go-Me和∠At-Go—Me无明显差异（P〉0．05）。结论双侧第二磨牙正锁[牙合]对下颌体长度、下颌第二磨牙处基骨弓宽度发育起到限制作用，髁突处于关节窝更前位，下颌角点位于矢状向更后位置。临床上对第二磨牙正锁[牙合]患者的治疗，治疗前应对髁突位移情况进行评估，以便正确诊断和提供最佳治疗方案。

Objective To study the effect of bilateral scissor bite of second molars on the growth and position of mandible and provide proper reference for correct orthodontic diagnosis and treatment of malocclusion. Methods 20 adult females with bilateral scissor bite of second molars were selected as experimental group. 30 adulte females with normal posterior occlusion were selected as control group. The subjects of both groups had high-angle Class II division 1 malocclusion. Lateral cephalograms were recorded before treatment. Jarabak cephalometric analysis and plaster model analysis were used to measure the differences between two groups. Results Compared with the control group, the length of mandibular body, the width of basal bone at second molar level,LN-S-Ar andLAr-Go-N were significantly smaller in the experimental group（P（0. 05）. S-N/Go-Me and ∠S- Ar-Go were larger in the experimental group （P〈0. 05）. However, there were no statistically significant difference in the height of mandibular ramus, the width of basal bone at the premolar and first molar level, S-Ar/Ar-Go, ∠N-Go-Me and ∠Ar-Go-Me between two groups （P〉0. 05）. Conclusions Bilateral scissor bite of second molars restricts the growth of mandibular body and basal bone width at second molar region, and the condyle is in a relatively anterior position, while G-onion is relatively posterior. Treatment with these patients requires analysis of condyle position to provide better treatment plan.