Hansen G K, Caruso J M, West V, Andreiko C A, Farrage J R, Jeiroudi M T
Department of Orthodontics, Loma Linda University School of Dentistry, California 92350, USA.
Aust Orthod J. 1997 Mar;14(4):242-6.
The rotation of the maxillary molars is considered important in the orthodontic treatment of malocclusions. In this study, a computer analysis program was developed to examine the rotations of maxillary molars, mandibular molars, and maxillary first premolars in casts of permanent dentitions with acceptable occlusions. Ninety-three sets of untreated 'acceptable occlusion' models from the collection of the Foundation for Orthodontic Research (FOR) were scanned on a flat bed scanner. The images were analysed using custom software. Measurements were made by relating maxillary first permanent molars to the midline, archform, opposite canine, and mandibular first permanent molars. The mandibular first molars and maxillary first premolars were also analysed and their rotations measured. The mean rotations of the maxillary first molars, measured as the angle between a line joining the tips of the buccal cusps and a line tangent to the appropriate archwire form (from Ricketts' Pentamorphic Arches) at the first molars, were 0.59 and -0.72 degree (positive values represent mesio-lingual rotations) for the right and left, respectively. For the mandibular molars, these means were 6.34 and 8.40 degrees, respectively. The mean differences in rotation between buccal cusp tips of maxillary and mandibular first molars in occlusion were 5.75 and 9.12 degrees for the right and left, respectively, with the mandibular being more mesio-lingually rotated. The differences between left and right were significant for all measurements. The present study brings into question the suitability of our present "straight wire" prescriptions in producing similar occlusions. It also suggests that scanning models for computer analysis may be a practical and precise way to measure similar rotations in untreated normal and treated occlusions.
上颌磨牙的旋转在错牙合畸形的正畸治疗中被认为很重要。在本研究中，开发了一个计算机分析程序，以检查具有可接受咬合的恒牙列模型中上颌磨牙、下颌磨牙和上颌第一前磨牙的旋转情况。从正畸研究基金会（FOR）的藏品中选取了93套未经治疗的“可接受咬合”模型，在平板扫描仪上进行扫描。使用定制软件对图像进行分析。通过将上颌第一恒磨牙与中线、牙弓形态、对侧尖牙以及下颌第一恒磨牙相关联来进行测量。还对下颌第一磨牙和上颌第一前磨牙进行了分析并测量其旋转情况。上颌第一磨牙的平均旋转角度，以连接颊尖的线与第一磨牙处与合适弓丝形态（来自Ricketts的五形态弓）相切的线之间的夹角来衡量，右侧和左侧分别为0.59度和 -0.72度（正值表示近中舌向旋转）。对于下颌磨牙，这些平均值分别为6.34度和8.40度。咬合时上颌和下颌第一磨牙颊尖旋转的平均差异，右侧和左侧分别为5.75度和9.12度，下颌的旋转更偏向近中舌向。所有测量中左右两侧的差异均具有统计学意义。本研究对我们目前“直丝弓”矫治方案在产生相似咬合方面的适用性提出了质疑。它还表明，扫描模型进行计算机分析可能是一种测量未经治疗的正常咬合和治疗后咬合中相似旋转的实用且精确的方法。
