【作者】 宋晓菲；

【导师】 殷玲；

【作者基本信息】 天津大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 利用高速牙科手机对陶瓷修复体进行口腔调磨是保证修复体按照预期寿命有效行使临床功能的关键环节。本文在国家自然科学基金的资助下,系统研究了牙科切削陶瓷调磨进程中的高速手机性能、陶瓷表面/亚表面质量及调磨参数优化设计等关键科学问题。论文取得以下创造性成果:设计了一种新型的模拟牙科调磨的二维体外实验装置,打破国外相关研究装置一维准静态局限。在此基础上,首次结合动态牙科切削实验,对高速牙科手机的性能参数进行了系统的测试和研究,揭示出牙科手机性能参数的主要影响因素及其变化规律,并确定了快速、精细两种典型牙科调磨进程中的高速牙科手机极限应用条件。利用压痕断裂力学理论,提出了牙科陶瓷产生横向裂纹的临界载荷模型。借助该模型与表面形貌观察法,揭示了牙科陶瓷在常规、快速、精细三种典型牙科调磨进程条件下的表面生成机理及表面损伤特征。研究结果表明,牙科陶瓷表面修复质量对车针金刚石粒度较敏感,而牙科调磨用量参数对改善牙科陶瓷的表面质量没有明显作用。借助有限元软件ANSYS参数化设计语言,提出一种牙科陶瓷调磨亚表面损伤预测模型,并通过实验验证其有效性。利用该模型,系统研究了牙科陶瓷调磨亚表面应力分布规律及损伤深度。研究结果表明,陶瓷修复体在调磨过程中,应力集中在磨粒即将离开材料处。研究还表明,最大主应力准则适合作为牙科陶瓷的损伤判据,牙科陶瓷调磨后的亚表面损伤深度与最大未变形切屑厚度线性正相关,且切削用量参数对其影响显著。结合牙科修复体调磨的临床特点,提出一种调磨参数优化设计方法。研究结果表明,该方法可以针对不同的实际临床条件和要求,有效、快速地对牙科调磨参数进行优化设计和求解。上述研究成果不仅为指导临床医师合理进行牙科调磨技术提供科学的理论依据,而且为改善牙科陶瓷修复体的临床使用性能开辟一条新的研究途径。更多还原

【Abstract】 Intraoral resurfacing of ceramic prostheses using dental handpieces/burs is the key in restorative dentistry because the durability of ceramic prostheses depends on the resurfacing processes and quality. This dissertation investigated the critical scientific issues during dental resurfacing of bioceramics using clinical high-speed dental handpieces and diamond burs. The following contributions and conclusions have been made:A novel 2-DOF in vitro dental cutting tester has been developed to simulate the clinical intraoral resurfacing operations. The performance of a high-speed dental handpiece was dynamically evaluated using the tester. The application limitations of the dental handpiece in rapid and micro-fine finishing of ceramic prostheses have been proposed. The results demonstrate that the process parameters, including depth of cut, feed rate, cutting direction and material properties were central factors in controlling the clinical performance of a dental handpiece.The surface integrity and the removal mechanism in dental resurfacing of ceramic prostheses were investigated based on indenting fracture theory and surface morphology analysis. Consequently, a mathematical expression of a threshold load of lateral cracking for dental resurfacing of dental ceramics was addressed, with which the removal mechanism could be predicted. The results show that the resurfaced surface quality was sensitive to the grit size of dental diamond burs, but insignificantly changing with the depth of cut and the feed rate of dental handpieces.The stress fields and the degrees of subsurface damage of ceramic prostheses in simulated dental resurfacing operations were investigated using finite element analysis (FEA). A finite element model was established to predict the stress fields and the depths of subsurface damage in ceramic prostheses as functions of the dental operational conditions. It shows the stresses were all centered at the grit exit point, and the depths of subsurface damage increased with both the depth of cut and the feed rate. The FEA predictions were in agreement with the experimental measurements.An approach of optimization of the complex dental resurfacing processes was presented based on the artificial neural network technology and sequential quadratic programming algorithm. It involved a multi-objective function considering both the material removal rate and the subsurface damage degrees to optimize the dental processes. An illustrative example demonstrates that the approach was fast and efficient for optimization of the dental process parameters.The above research outcomes have provided the fundamental data and scientific base to restorative dentistry on proper intraoral dental resurfacing of ceramic prostheses.更多还原