下颌全牙弓后移量及最后界的测量

目的：研究下颌牙弓的有效后移量及找寻下颌牙弓移动的后界。方法：选取涉及拔除下颌第三磨牙或下颌第三磨牙缺失的病例18例（男6例,女12例）。采用种植支抗牵引下牙弓向远中,治疗完成时所有病例均明确到达下颌牙弓后界,即下颌第二磨牙远中到达下颌升支前缘软组织交界处。应用治疗前后的曲断片测量下颌第二磨牙远中到升支前缘的距离。结果：下颌第二磨牙后移量为（3.49±1.21）mm;治疗后磨牙后间隙的长度为（4.43±0.97）mm。结论：下颌牙弓可确定性地实现整体后移;最大后移量由磨牙后间隙的长度决定;其最后界止于下颌第二磨牙远中与下颌升支前缘软组织交界处。

Measurement of the distal traction distance of the mandibular dentition and the assessment of the posterior limit of the mandibular arch

Objective To study the effective tracting distance of the mandibular dentition and to find the posterior boundary of the lower arch during the distalizing of the mandibular dentition.Methods 18 cases were selected（6 males,12 females） with mandibular third molar extracted or missing.Skeletal anchorage implants were used to distalize the mandibular dentition to the posterior limit of the dentition.The distance between the mandibular second molar and the ramus was measured on panoramic radiographs at pretreatment and posttreatment.All the data were analyzed statistically.Results The moving distance of mandibular molar was（3.49±1.21）mm.After treatment,the distance between the mandibular second molar and the ramus was（4.43±0.97）mm.Conclusion The mandibular dentition can be distalized by orthodontic treatment,teeth movement is limited and restricted by the thickness of the soft tissue prior to the ramus.