基于Typodont模型的MDD与MBT矫治器排齐阶段切牙三维移动变化研究

The Typodont Model Based Investigation on Three-Dimensional Movement of Incisors in Alignment Stage when Applying MDD and MBT Orthodontic Brackets

在Typodont模型上分析MDD与MBT矫治器排齐阶段切牙的三维移动变化,为固定矫治器的改良及应用提供参考。以安氏Ⅱ类1分类错(牙合)为标准,硅橡胶取印模后,加入树脂牙和蜡制作相同的Typodont模型10副,MDD和MBT每组各5个样本。采用ATOS流动光学三维扫描仪,获得初始的三维数字化模型,以Typodont颌架底座定位确定数字化水平向、矢状向及垂直向三维坐标系。45℃恒温水浴下依次使用0.36、0.41、0.46 mm镍钛圆丝排齐20 min,每次水浴后扫描模型获得新的三维数字化模型。Geomagic软件以三维坐标系为重叠标志将每次水浴后的三维数字化模型与初始数字化模型重叠,重叠后通过色图分析得出8颗切牙近远中切角点发生的三维移动变化。应用SPSS17.0软件包对实验数据进行t检验。结果表明:水平向,37%的标志点负方向移动,75%的数据有统计学差异(P<0.05),其中MDD组移动变化小的占81.5%;矢状向,91.7%的标志点唇向移动,83.4%的数据有统计学差异(P<0.05),其中MDD组移动变化小的占73.3%;垂直向,所有标志点均为(牙合)向移动,86.1%的数据有统计学差异(P<0.05),均为MDD组移动变化小。安氏Ⅱ类1分类错(牙合)排齐阶段使用MDD矫治器具有轻力矫治的特点,并可缓解切牙唇向、(牙合)向的不利移动。

This project is purposed to compare three-dimensional movement of incisors in typodont models when applying MDD and MBT orthodontic brackets in the alignment stage,and to provide reference to the improvement and clinical application of fixed orthodontic appliances.According to the standard Class Ⅱ division 1,impressions of malocclusion were taken with silicone rubber impression material,followed by addition of wax and resin teeth into the impressions.Ten identical models were made in this work.The models were randomly divided into groups MBT and MDD（5 for each group）.Digital models were obtained by scanning with the three dimensional optical scanner ATOS.The horizontal vertical and sagittal three-dimensional system was then established.Nickel titanium round wires with diameter of 0.36,0.41 and 0.46 mm were applied in turn to align the teeth while bathed in a constant temperature of 45 ℃ water for 20 minutes.Scanning was done to obtain a new digital model following each water bath.Geomagic software was used to overlapped the three-dimensional digital models that were taken before and after each water bath.The three-dimensional system was the overlapping references when Geomagic software overlapped the models.The corner points of eight incisors changes were quantified by using the Color map.The data was analyzed for t test using SPSS17.0 software package.Horizontal： 37% of the sign points moved in the negative direction,75% of the data was significantly different（P 〈0.05）,81.5% of these changes were less in the MDD group.Sagittal： 91.7% of the sign points moved labially,83.4% of the data was significantly different（P 〈0.05）,73.3% of these changes were less in the MDD group.Vertical： All sign points moved occlusally,86.1% of the data was significant different（P 〈0.05）,the MDD group changed less.MDD orthodontic bracket has the characteristic of light force in the alignment stage,which can be applied to class II division 1 malocclusion to prevent incisors from moving labially and occlusally in the alignment stage.