The purpose of this study was to compare orthodontic treatment outcomes in Chinese patients with borderline problems treated with and without extractions. Methods: Records of 39 borderline patients treated at the Faculty Clinic of the Peking University Orthodontic Department were evaluated retrospectively by 5 associate professors. Sixteen patients had been treated without extractions, and 23 had 4 first or second premolars extracted. Each judge evaluated the posttreatment records independently for tooth alignment, overbite, overjet, midline symmetry, lateral occlusion, and facial profile, and rated them on a scale from 1 to 5. Results: The only statistically significant difference between the extraction and nonextraction groups was for facial profile, with the judges preferring the extraction profiles. Fifteen soft-tissue cephalometric variables were measured to determine the source of the difference, and 6 showed statistically significant differences. When profile changes from pretreatment to posttreatment were examined, significant differences in treatment-associated changes between extraction and nonextraction groups were all related to the lower lip and chin. Conclusions: In this sample of Chinese borderline orthodontic patients, Chinese clinicians had a statistically significant preference for the facial profiles of the extraction patients, but no statistically significant preferences for tooth alignment, overbite, overjet, midline symmetry, or posterior occlusion. Extraction treatment increases the inclination of the chin and reduces protrusion of the lower lip compared with nonextraction treatment, and this might explain the difference.

目的：调查上切牙内收过程中牙槽骨的增生与吸收情况。方法：以55例拔牙治疗病例治疗前、治疗后、及随访期的头颅侧位片为研究样本，测量他们在这3个阶段切牙的位移以及其牙根前方和后方牙槽骨的厚度变化及牙槽突总厚度的变化情况。测量方法采用腭结构重叠法，以治疗前的前颅底平面为参照平面建立同一坐标系，双人定点取均值的方法在计算机上完成测量及重叠计算。结果：上切牙阻力中心治疗后向腭侧移动了1.8mm（P<0.001），向上移动了0.4mm（P>0.05）。阻力中心水平的唇侧牙槽骨厚度增加了0.2mm（P<0.01），腭侧牙槽骨厚度减小了0.8mm（P<0.001）；随访期切牙阻力中心向唇向复发了0.8mm（P<0.01），阻力中心水平的唇侧牙槽骨厚度相应减小了0.2mm（P<0.05），但腭侧牙槽骨厚度却并没有明显的增加。结论：在上前牙唇腭侧向移动的过程中，牙槽骨的生物学改建是以骨吸收为主，骨增生十分有限。

In the Begg Technique, factors controlling the anterior intrusive force provided by the archwire have yet to be fully clarified. The rationale for bite opening with very light forces, the effect of Class II elastics on intrusive Force magnitude and the intrinsic qualioy of "Australian" wire in bite opening are examined in this paper. A formulais is presented which allows the intrusive force that archwir exert in different individuals to be predicted. The values derived from the formula were compared with cose model measurements. it was found that the intrusive force of the archwire was afreeted by the length of th e indi vidual dental arch. The magnitude of this in trusive force was seen to increase gradually during the period of bite opening and appeared to be related to the use of Class II elastics. The study revealed factors which aiffected the magnitude of the intrusive force.

目的 比较患者拔牙与不拔牙正畸治疗在牙齿排列、咬合关系、面形和疗程方面的差异。方法 5位正畸专家根据治疗前资料挑选出的既可采用拔牙，又可采用不拔牙治疗的39例错畸形患者为研究对象。评价患者的治疗效果，再根据患者实际是否采用拔牙治疗进行分组比较。结果 拔牙组与不拔牙组患者，在牙齿排列、覆覆盖、中线、侧方咬合关系方面的评分及平均疗程上均无显著性差异（P>0.05）；只有侧貌美观的评分，拔牙组高于不拔牙组，两组间有显著性差异（P=0.001） 。结论 对于临界病例，拔牙与不拔牙治疗在牙齿排列、咬合关系方面都能在基本相同的治疗时间取得类似的疗效；但拔牙患者，无论是拔第一前磨牙还是拔第二前磨牙，都比不拔牙患者获得了更加令人满意的面形。

目的：探讨头影测量标志点在治疗前后位置的改变对角度测量值变化的实际影响。方法：选用48例青少年安氏I类及类错牙合患者治疗前后的头颅侧位片，以正畸临床常用的4个具有代表性意义的角度测量项目SNA、ANB、NAPg和UIˆSN为因变量，以构成这些角度的头影测量标志点为自变量进行逐步回归分析，从入选回归方程的标志点及其决定系数大小判断各标志点位移对相应角度测量值的影响。结果：上述4个角度所作回归方程的决定系数分别为0.96，0.95，0.39和0.99。结论：除了NA Pg，其它3个角度的变化基本能反映出颌骨及牙齿在矢状方向的位置改变，但SNA 角的变化在一定程度上同时受N点水平向位移的影响，使其反映A点水平向位置改变的可靠性受到影响。