根管弯曲度的曲线分析和几何学测量

Curve analysis and geometric measurement of root canal curvatures

目的:研究弯曲根管的形态学特点。方法:按照Nagy的弯曲根管分型法,将根管分为I型、C型、J型及S型共4型。从离体牙中各选1例典型者,拍摄其颊舌向与近远中向的数字化X线片(插针片);Photoshop7.0、CorelTRACE10软件对图像作预处理,UG NX V1.0软件提取根管长轴的2D曲线,根据2D曲线构建出根管长轴的3D曲线,然后对其进行曲线分析及几何学测量。结果:I型根管曲率较小,曲率波动平缓;C型弯曲根管的曲率峰值在根管中部,曲率向两侧逐渐减小;J型根管的曲率分布集中在根尖部,根管颈1/3、中1/3部为曲率平坦区;S型根管存在1个弯曲拐点,拐点两侧各有1个反向的曲率峰值。同一根管的2D根管长轴与3D根管长轴测得的几何参数值存在差异。结论:根管长轴上的每一个点都有1个曲率值与切向量,不同弯曲类型的根管,其曲率分布具有不同的特点,仅以1～2个参数来衡量1个根管的弯曲度是不全面的。

PURPOSE: To study the anatomical features of curved root canals. METHODS: According to Nagy's classification,the root canals were divided into 4 types:type I(straight),type C (continuously curved), type J (apically curved) and type S(multicurved). Each type had a sample selected from extracted permanent teeth.Digital radiographs were taken at buccolingual and mesiodistal directions with a K-file inserted into the root canal.The images were treated by Photoshop7.0 and CorelTRACE10 softwares, after that a CAD/CAM software UG NX V1.0 was applied to extract the 2D curves of the root canal axis from the images,then the 3D curves of the root canal axis were built up accordingly.The curvature of the curves was analysed and the geometric parameters were measured by UG. RESULTS: The curvature values of type I root canal were very low; the curvature of type C root canal reached a peak on the middle part,it decreased slowly towards the two ends; type J root canal had a curvature peak near the root apex , and the middle 1/3 and neck 1/3 parts of the root canal were 'curvature flat zones'.Type S root canal had a curvature inflection,and beside it were 2 curvature peaks at opposite directions.The geometric parameter values of the same root canal's 2D and 3D axis were different. CONCLUSION: Each point on the root canal axis had a curvature value and a vector of tangent, different root canal forms had different rules of curvature distribution, just 1 or 2 parameters couldn't describe a curved root canal completely.