第一恒磨牙牙冠的三维几何形态学分析

Three-dimensional Geometric Morphometric Analysis of First Permanent Molar Crowns

目的:运用三维几何形态学方法研究上、下颌第一恒磨牙牙冠外形,量化与比较牙冠间的三维形态差异。方法:三维激光扫描100对中国青少年牙齿石膏模型,男、女各50对。运用主成分分析对磨牙的形状参数进行评估,借助薄板样条(TPS)变形网格探寻各个主成分所代表的牙冠解剖学意义。结果:上、下颌第一恒磨牙前5个主成分贡献了70%~80%形状变异,前2个最重要的主成分与牙冠的大小和牙尖点的相对位置有关。其大小显著相关(r2=0.703),男性的磨牙比女性更大(上、下颌分别为2.68%和1.66%),但无明显的两性分化。结论:上、下颌第一恒磨牙的形状变化主要表现在牙冠大小、尖窝高度和牙尖点的相对位置。下颌第一恒磨牙远中尖的变异度最高。两性分化仅限于牙冠的大小,形状并无明显差异。

Objective：To research the shape of the first permanent crowns,and to quantify and compare the three-dimensional morphological differences between crowns.Methods：One hundred pairs of Chinese juvenile dental plaster models were 3 Doptical scanned,including fifty pairs of males and fifty pairs of females.Principal component analysis was performed to assess the shape parameters.With the help of thin plate spline（TPS）,the anatomical significance of each principal component was explored.Results：The first five principal components of the first upper and lower permanent molars comprised almost 70-80% of the molar shape variations,and the first two most important principal components were related to the mesiodistal-buccolingual ratios and the relative cusp positions.The tooth size was significantly correlated（r2=0.703）,and the male molars were larger than the female molars（2.68% and 1.66%for the upper and lower molars,respectively）,but no shape dimorphism was observed.Conclusion：The shape variations of upper and lower permanent molars were related to mesiodistal-buccolingual ratios,heights between teeth tips and fossea,and relative cusp positions.Distal cusps of lower permanent molar showed the highest variability.Sexual dimorphism was limited to size difference and the shape variation was weak.