Hofmann Elisabeth, Medelnik Jürgen, Keller Thomas, Steinhäuser Stefanie, Hirschfelder Ursula
Department of Orthodontics, University Hospital, Erlangen-Nuremberg, Erlangen, Germany.
J Orofac Orthop. 2011 Mar;72(1):33-44. doi: 10.1007/s00056-010-0005-0. Epub 2011 Mar 11.
Precise, three-dimensional localization of impacted maxillary canines is central to their clinical management. Predicting precisely the crown's mesiodistal width is paramount in planning orthodontic treatment. The aim of this study was to verify the exact mesiodistal width of impacted canines via MSCT (multislice spiral computed tomography) examinations.
3D MSCT images from 17 patients with a total of 24 impacted maxillary canines were taken to obtain the largest mesiodistal diameter using mesial and distal contact points. All existing maxillary canines were included in this study. Mesiodistal tooth width was also determined using callipers on a plaster model after canine eruption. Each measurement was taken twice by 3 observers after a 10-day interval. Statistical analysis entailed calculating and comparing the systematic error, intrarater and interrater standard deviations (Deming regression and ANOVA with random effects).
Comparison of the different methods revealed good agreement between the pre-eruption and post-eruption values regarding the canine's mesiodistal width. Total standard deviation was 0.16 mm for values obtained from MSCT measurements and 0.12 mm for those taken with callipers. For both methods intrarater measurement error differed by a factor of 2 (repeatability; model versus MSCT: 0.07 mm versus 0.12 mm), while interrater deviation did not differ significantly (reproducibility; model versus MSCT: 0.10 mm versus 0.10 mm). The reproducibility of our measurements whether taken on the model or with CT was below biological variability.
The volumetric data from an MSCT system gives highly accurate information on the mesiodistal width of displaced canines.
对上颌埋伏尖牙进行精确的三维定位是其临床治疗的关键。在正畸治疗计划中，精确预测牙冠的近远中宽度至关重要。本研究的目的是通过多层螺旋计算机断层扫描（MSCT）检查来验证埋伏尖牙的确切近远中宽度。
对17例患者共24颗上颌埋伏尖牙进行了三维MSCT扫描，通过近中及远中接触点获取最大近远中直径。本研究纳入了所有现存的上颌尖牙。在尖牙萌出后，还使用卡尺在石膏模型上确定近远中牙宽度。3名观察者在间隔10天后对每项测量进行两次测量。统计分析包括计算和比较系统误差、观察者内和观察者间标准差（Deming回归和随机效应方差分析）。
不同方法的比较显示，在尖牙近远中宽度方面，萌出前和萌出后的值具有良好的一致性。MSCT测量值的总标准差为0.16mm，卡尺测量值的总标准差为0.12mm。两种方法的观察者内测量误差相差2倍（重复性；模型测量与MSCT测量：0.07mm对0.12mm），而观察者间偏差无显著差异（再现性；模型测量与MSCT测量：0.10mm对0.10mm）。我们在模型上或通过CT进行测量的再现性低于生物学变异性。
MSCT系统的容积数据能提供关于移位尖牙近远中宽度的高度准确信息。
