义齿数字化修复牙齿分割与标准牙冠定位技术研究

发布时间：2018-04-22 13:13

本文选题：口腔修复 + 口腔CAD/CAM系统　；参考：《广东工业大学》2017年硕士论文

【摘要】：随着计算机技术、信息技术和图形学技术的发展,口腔数字化修复技术凭借高效率、高精度和智能化的优势,正逐步取代传统的口腔修复体手工设计、制造方式,掀起口腔修复领域的一次技术革命。针对国外口腔CAD/CAM系统垄断国内市场以及国内义齿数字化修复技术存在交互多、效率低、精度差等问题的现状,本文从计算机图形学和口腔修复学的结合应用出发,深入研究了牙齿分割和标准牙冠定位这两项关键技术,提出了新方法。具体内容和成果如下:(1)针对三维牙颌模型直接进行牙齿分割而不对齿间融合区域进行处理会存在精确度较差、缺失侧面形状的问题和现有牙齿形状建模方法交互多、效率低的问题,提出一种基于特征线分段技术的牙齿分割算法。根据曲率信息筛选特征区域并采用形态学算法提取牙列特征线;结合特征线分段和分支点匹配算法以及形态学膨胀操作实现齿间融合区域的自动识别;利用匹配的分支点对齿间孔洞搭桥修补,实现牙齿形状的自动恢复;提取齿间龈缘线,然后以所有龈缘线作为牙齿分割线分离出单颗牙齿。实验结果表明,该算法不仅能准确分离出具有侧面形状的单颗牙齿,而且避免了牙齿形状建模时的交互操作,提高牙齿分割效率60%~90%。(2)为便于在口腔CAD系统中对义齿进行缩放、定位和匹配等设计工作,提出一种简单、可靠的数字化牙体形位参数测量方法。首先通过观察和分析,确定以近远中方向对称面、颊(唇)舌方向对称面和牙尖所在水平面3个面作为建立牙齿定位约束的基准面,并从实用角度考虑,确定以近远中径和颊(唇)舌径2个水平方向尺寸作为牙齿的形状参数;然后,改进了牙体外形高点的识别方法,通过设置动态阈值保证了识别结果的可靠性;最后,通过识别5个外形高点计算出相应的形位参数。(3)在全冠、全冠桥以及嵌体等修复体设计中,从系统数据库调入的标准牙冠被用来模拟缺失牙的位姿并作为修复体的外表面(或颌面)。针对现有标准牙冠定位技术操作复杂、效率低、效果差的问题,提出一种简便高效的解决方案:在调入参考对象后首先调整基牙坐标系,然后计算出标准牙冠与参考对象的形位参数,再通过齐次坐标变换对标准牙冠的尺寸和位置进行调整。进一步,根据邻牙和基牙约束信息将标准牙冠定位分为四类情形:根据左右邻牙进行定位、根据单颗基牙进行定位、根据基牙和一侧邻牙进行定位和根据嵌体预备体进行定位,这四种情形涵盖了修复体设计定位的各种场景。对此,文中分别给出详细的实现过程。实验结果表明,定位后的标准牙冠尺寸与基牙较为协调,近远中面与邻牙自然贴合,牙齿位姿较为合理。
[Abstract]:With the development of computer technology, information technology and graphics technology, with the advantages of high efficiency, high precision and intelligence, digital prosthesis technology is gradually replacing the traditional manual design and manufacturing method of dental prosthesis. Set off a technological revolution in the field of prosthodontics. In view of the foreign oral CAD/CAM system monopoly domestic market and the domestic denture digital restoration technology has many problems, such as interaction, low efficiency, poor precision and so on, this paper starts from the combination of computer graphics and prosthodontics. Two key technologies of tooth segmentation and standard crown positioning are studied and a new method is proposed. The specific contents and results are as follows: 1) in view of the three-dimensional dental model, it is difficult to segment the teeth directly without processing the fusion area between teeth, and the problem of missing side shape and the interaction between the existing methods of tooth shape modeling are many. A tooth segmentation algorithm based on feature line segmentation is proposed. According to the curvature information, the feature region is selected and the dentition feature line is extracted by morphological algorithm, and the feature line segment and branch point matching algorithm and morphological expansion operation are combined to realize the automatic recognition of the fusion region between teeth. The matching branch points were used to repair the holes between teeth to achieve the automatic restoration of the tooth shape. The gingival margin line was extracted and the single tooth was separated from all the gingival margin lines. The experimental results show that the algorithm can not only accurately separate a single tooth with side shape, but also avoid the interactive operation of tooth shape modeling, and improve the efficiency of tooth segmentation. In this paper, a simple and reliable method for measuring the profile and position parameters of digital teeth is presented. First, through observation and analysis, it is determined that the symmetrical plane in the direction of the proximal Chinese side, the symmetrical plane of the cheek (lip) and the horizontal plane of the cusp are used as the datum for the establishment of the tooth positioning constraint, and considered from the practical point of view. The shape parameters of the teeth are determined in the two horizontal dimensions of proximal midway diameter and buccal (lip) diameter. Then, the recognition method of tooth contour height is improved, and the reliability of the recognition result is ensured by setting dynamic threshold. The corresponding shape and position parameters are calculated by identifying the five height points.) in the design of crown, crown bridge and inlay, etc., Standard crowns from the system database are used to simulate the posture of missing teeth and act as the external surface of the prosthesis (or maxillofacial canal). Aiming at the problems of complex operation, low efficiency and poor effect of the existing standard crown positioning technology, a simple and efficient solution is proposed: adjusting the abutment coordinate system first after the reference object is transferred. Then the shape and position parameters of standard crown and reference object are calculated and the size and position of standard crown are adjusted by homogeneous coordinate transformation. Furthermore, according to the constraint information of adjacent teeth and abutment teeth, the standard crown positioning was divided into four categories: location based on left and right teeth, single abutment, abutment and side adjacent teeth, and inlay preparation. These four scenarios cover the various scenarios of the fix design location. In this paper, the detailed implementation process is given. The experimental results show that the standard crown size is more compatible with the abutment teeth, and the proximal and middle surfaces are naturally aligned with the adjacent teeth, and the position and posture of the teeth are more reasonable.
【学位授予单位】：广东工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R783;TP391.7

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