3D形貌牙体精确制备基础理论与关键技术研究

Tooth preparing is the basic clinical operation of treating dental hard tissue diseases. Its purpose is to remove the lesion and prepare the remaining tissue to suitable 3D topography for restoration. The tooth prepared completely is called tooth preparation. The common tooth preparing operation is the visual manual mechanical grinding, by means of which, the 3D topography of the planned tooth preparation is difficult to be accurately obtained because it is affected by physician experience, operation technology, operation stability and subjective factors. So, they directly affect the quality of treatment. Researches shows that the effect of specific parameters picosecond laser cutting dental hard tissue are surface fairing and clear point clear line angle. If it is combined with CNC galvanometer technology, it is expected to achieve high precision tooth preparing. Project is intended to study the basic theory and key technology of high precision tooth preparing with the numerical control picosecond lasers and the quantitative predict of tooth preparation 3D topography. The study includes ①the quantitative design of crown preparation 3D topography, ②error control of ablation depth and degree of polymerization of tooth preparation when the numerical control picosecond laser cutting dental hard tissue, ③the critical process parameters of ablation rate, ④ the effect of ablation quality and rate by cooling control process for pulp chamber temperature, ⑤the method of analyzing the plasma composition of dental hard tissue and its dissipation mechanism, ⑥quantitative evaluation of 3D topography precision of tooth preparation. The relative basic theory and key technology of the accurate 3D tooth preparing will be obtained more systematic study, which lays a solid foundation for developing automatic clinical tooth preparing system.

牙体预备是治疗牙齿硬组织疾病的基本临床操作，目的是去除病变，将剩余组织制备成适宜修复的3D形貌，预备完成的牙齿称为预备体。常用的牙体预备操作为目测手工机械磨削，受医生经验、操作技巧、操作稳定性和主观因素影响，很难准确获得预设的预备体3D形貌，直接影响治疗质量掌控。研究表明，特定参数皮秒激光切削的牙体硬组织表面光顺、点线角清晰明确，如结合数控振镜技术，有望实现高精度牙体预备。项目拟针对预备体3D形貌定量预测、数控皮秒激光高精度牙体制备的基本理论和关键技术展开研究。研究内容包括①全冠预备体3D形貌定量设计②基于数控皮秒激光的牙体硬组织切削深度、预备体轴面聚合度误差控制③制备效率关键工艺参数④牙髓腔温度风冷控制工艺对切削质量、效率的影响⑤牙齿等离子体成分分析及消散机制⑥预备体3D型面精度定量评价。较系统地研究3D形貌牙体精确制备相关基础理论和关键技术，为研发自动化临床牙体预备系统奠定理论基础。

牙体预备，是口腔医生治疗各类牙齿疾病最常用和基本的方法。目前只能靠手工操作来完成，难以达到临床操作规范提出的标准要求，医疗质量难以控制。研究表明，特定参数皮秒激光切削的牙体硬组织表面光顺、点线角清晰明确，如结合数控振镜技术，有望实现高精度牙体预备。项目拟针对预备体3D形貌定量预测、数控皮秒激光高精度牙体制备的基本理论和关键技术展开研究。主要研究内容包括①全冠预备体3D形貌定量设计②基于数控皮秒激光的牙体硬组织切削深度、预备体轴面聚合度误差控制③制备效率关键工艺参数④牙髓腔温度风冷控制工艺对切削质量、效率的影响⑤牙齿等离子体成分分析及消散机制⑥预备体3D型面精度定量评价。课题组通过四年的努力，目前已建立一套完整的全冠预备体3D形貌设计流程，并开发了专用的设计软件；通过对激光的重要参数（如功率、重频、光斑直径等）进行排列组合，在不同年龄、不同性别、不同牙位、不同牙体硬组织进行大量实验，探索出二维切削牙本质和牙釉质时激光扫描层数与切削深度之间定量关系曲线呈现线性非直线上升趋势，通过线性拟合得出最大切削深度范围内脉冲层数与切削深度的定量关系函数式分别 为d=10.547n-7.5465；R2=0.9796；d=10.16n-6.04；R2=0.9778。三维切削正方形窝洞的实际深度与理论深度的差值不等，单次进给量越小，则差值越小，即以每切削5层步进45µm设定Z轴的进给速度，切削深度精度可控制在1.91µm和2.25µm。根据空气动力学原理和激光切削机理，选用超音速喷嘴转送冷空气降温的方式，达到有效的降温效果，在切削过程中，可使温度控制在37度之内。预备体3D形貌型面精度控制在微米级。通过该项目的支持，较系统地研究3D形貌牙体精确制备相关基础理论和关键技术，为研发自动化临床牙体预备系统奠定了理论基础。