【作者】 安涛；

【导师】 廖文和；

【作者基本信息】 南京航空航天大学 ， 航空宇航制造工程， 2008， 博士

【摘要】 CAD/CAM技术在口腔修复领域的广泛应用,使得口腔修复技术实现了由手工操作向自动化、智能化方向的跨越。基底桥修复体是口腔修复体的重要组成部分,本文结合口腔临床的应用需求,以基底桥修复体为研究对象,以基底桥的设计流程为研究主线,系统研究了基底桥修复体数字化设计的相关基础理论、方法及关键技术。本文主要研究内容和成果如下:(1)提出了基底桥网格模型数据预处理算法。为基底桥各组成部分的STL文件重建了拓扑结构,采用以三角片为单位的思想,将冗余点去除和拓扑结构的创建统一在一个过程中完成,节省了创建中间结构所需的时间,可以快速查找三角网格的点、线、面及其一维邻域等基本信息,以及孔洞、边界等拓展信息,较以往算法可以节省20%-50%的时间,实现了基底桥三角网格模型的快速半边拓扑结构重建。(2)建立了标准桥体/连接体数据库。基于标准全冠模型,设计了28颗标准桥体数据并组成了标准桥体数据库,其中模型外形符合临床要求、表面光滑、数据完整,而且基于国人标准全冠设计,因此更加适合中国人的牙齿形态;根据磨牙与切牙近远中面形态的差异,设计了2种不同截面形状的标准连接体,使得设计更加人性化,基底桥的形态更加合理,实现了标准桥体/连接体数据库的建立。(3)提出了桥体/连接体定位算法:首先计算整副模型网格顶点的曲率,利用趋势面分析的方法获得了咬合平面;之后根据两侧内冠的位置,利用体积加权法和咬合平面确定标准桥体的位置及角度,完成自动定位;最后通过手工微调,确定模型的精确位置。最终定位结果可以满足实际临床的需求,完成桥体和连接体的定位只需两分钟左右,实现了桥体和连接体的精确定位。(4)采用比例变换的方法完成了桥体的整体变形调整;提出了基于面积约束的连接体模型变形设计算法,实现了连接体截面形状调整;提出了基于梯度域的桥体　面局部变形设计算法,通过线性Laplacian变形、旋转分量叠加和微分坐标系更新三个步骤的不断迭代,使得初始网格不断向目标网格逼近,变形后的网格光顺,并可以保持原始网格的细节特征,操作过程简单、直观,实现了桥体和连接体的变形设计。(5)提出了“交线提取—网格裁剪—网格缝合—网格光顺”的基底桥模型整体融合算法。提出了基于拓扑的网格交线提取算法,实现了两个三角网格交线的快速提取;提出了基于交线的三角网格裁剪算法,完成了三角网格准确、快速的裁剪;提出了通过直接连接边界点构造过渡三角片实现网格缝合的方法,将两个独立的三角网格缝合为一个整体;利用Taubin光顺对网格过渡区域进行光顺,保证了过渡区域的自然光滑,实现了基底桥各组成部分的融合,得到了基底桥的最终数字化模型。(6)设计了基底桥数字化设计系统的总体设计框架,将整个设计系统划分为内冠设计、桥体设计和连接体设计等三个主要部分,阐述了各个部分在系统中的作用;详细说明了基底桥修复体的总体设计流程。结合口腔修复临床的实际需要,开发了口腔基底桥数字化设计系统原型软件,针对实际病例,完成了多例基底桥修复体的设计,取得了良好的效果。更多还原

【Abstract】 With the CAD/CAM technologies widely used in dental medical treatment, the dental repair process can be finished with computer system, which is much more automatic and smarter than the traditional method. The PFM fixed bridge framework is one of the most important parts of the dental restoration. Combined with the demands of dental clinic, system structure, relevant theories and key technologies are studied deeply in this dissertation and the PFM fixed bridge framework CAD prototype software is developed. The main contents and achievements are as follows:1. The half-edge topological reconstruction algorithm based on Red-Black tree is presented to efficiently reconstruct the topological structure of the bridge which consists of several mesh models. The algorithm takes the triangular facet as unit. Filtering the redundant vertexes and searching neighbor information are merged into one process. The vertices, edges and facets and many other information can be rapidly checked with this topological structure.2. The standard bridge and connector database is built. 28 standard bridge models are designed based on modifying the standard crowns. They are beautiful and smooth, and moreover, fit the Chinese very well. Two kinds of standard connectors are designed based on the difference of the molar and the incisor, which have different cutting plane shapes for different uses.3. The precise location algorithm is presented to locate the bridge and connector to the perfect positions. Firstly, the curvature of every vertex is computed, and the occlusal plane is located based on the trend plane analysis. Secondly, the model is located to the rough position automatically based on the volume weight method of the coping crowns. Finally, the model is located to the perfect position with manual fine tuning.4. The scale transformation is used to realize the bridge global deformation and the algorithm based on area restriction is put forward to realize the connector cutting plane shape deformation. The deformation algorithm based on gradient is presented to realize the bridge’s maxillofacial local deformation. The algorithm iterates the linear Laplacian deformation, rotation extraction and differential coordinate update to deform the original mesh to the target mesh step by step. The deformed mesh keeps smooth and retains the detail feature very well.5. The mesh mergence algorithm is presented to merge several separate parts into a whole one, which consists of four steps: intersection line extraction, mesh cutting, mesh fixing and mesh smoothing. The intersection line extraction algorithm based on the topological structure get the line rapidly. The meshes are cut based on the line, and then connected together with the triangles constructed with the boundry points. Finally, the transitional regions are smoothed with Taubin smooth algorithm. After all parts are merged, the design process of the PFM fixed bridge framework is accomplished.6. The total development framework of the PFM fixed bridge framework CAD system is presented. The system includes three main parts: design of the coping crowns, design of the bridge and design of the connectors. The function and design process of every part are also expatiated. Based on the practical demands in clinical prosthodontics, the dental PFM fixed bridge framework CAD prototype system is developed. And several special patients’bridges are designed accurately and efficiently with this system.更多还原