基于磨损行为时间特性的齿科玻璃陶瓷微结构调控研究

Dental ceramics are widely used in clinical physicians because of their excellent biocompatibility and good performance. Porcelain fracture and high wear to opposing tooth due to repeated load cycles are regarded as significant problems. In dental research, previous scholars tend to study the wear behavior and mechanical properties of different materials in a certain time point. Nevertheless the classical theory of friction considers the wear process of friction pair would show a wear curve consisted of three stages such as "running- in stage ", "stable wear stage" and "severe wear stage”. Our research group showed the three stages in dental ceramics wear, meanwhile many factors affect the progress of each stage. As a consequence, it is unreasonable to compare wear behavior of ceramic materials at a fixed point, since the ceramics are prone to be in different wear stages. Choosing dental glass ceramics as the research object, our research group tend to change the crystal phase fraction, crystal size and stress state of the microstructure from the perspective of wear behavior of time characteristics to shorten "running in stage" and to extend "steady wear stage ", with the aid of oral fatigue wear testing machine, 3D Profiling, scanning electron microscope, X-ray diffraction, differential scanning calorimetry, nanoindentor and other means. We expect to explore a new way for the improvement and research of dental ceramic materials.

齿科瓷修复材料因具有优良生物相容性和极佳美学效果，已被广泛应用于牙齿牙列缺损的修复，但咀嚼循环磨损造成的瓷崩裂及对颌牙过度磨耗是目前临床面临的主要问题。以往研究均是设定某一咀嚼循环次数后比较齿科陶瓷的磨损行为和力学性能，而经典摩擦学理论认为材料磨损具有跑和期、稳定期和剧烈破坏期“三阶段特征”。我们近期研究证实齿科陶瓷磨损也存在这种非线性动态演变过程，且三阶段进程受多种因素影响会有所变化。因此，基于设定循环次数评价齿科瓷材料的磨损性能，有可能将处于不同磨损期的材料相比较，不尽科学合理。本课题拟以齿科玻璃陶瓷为研究对象，借助口腔疲劳磨损实验机、3D 形貌仪、扫描电镜、X射线衍射、差热分析、纳米压入仪等手段，通过改变晶体相分数、尺度、微结构应力状态等，以“缩短跑合期”、“延长稳定期”为目标，从磨损行为时间特性这一全新角度，对其微结构进行有效调控，为齿科陶瓷材料的性能改进及研发探索一条新的途径。

本实验选用拥有良好的晶化能力的二硅酸锂玻璃陶瓷为研究对象，从晶体结构的调控角度出发，在保持其力学性能的前提下，改善体系的“摩擦学特性”，以缩短“跑合期”，延长“稳定磨损期”，从而降低修复体的早期失败率。以二硅酸锂玻璃陶瓷块作为原始材料，融化后获得块体基础玻璃。利用示差扫描量热法分析基础玻璃的结晶特征，热处理得到四组晶体体积分数相近、晶体尺寸不同的玻璃陶瓷,编号为为G1-G4。将商品陶瓷利用热压铸技术制作规格相同的二硅酸锂铸瓷(GC-P),同时将商品陶瓷切片（GC-O）采用G4组的热处理方式进行晶化，两组同时作为对照组。利用三点弯技术测定抗弯强度，利用纳米压痕法测定硬度和弹性模量。利用口腔疲劳磨损试验机进行循环磨损实验，利用三维形貌仪测量试件磨损体积的变化。利用扫描电镜分析不同磨损阶段微观形貌。尝试对二硅酸锂玻璃陶瓷进行退火和250℃硅油淬火处理,并进行XRD测试。XRD图谱显示两组样品主晶相都为二硅酸锂相。探究不同退火处理对于二硅酸锂陶瓷力学性能的影响。六组陶瓷显示主晶相为二硅酸锂晶体，同时含有少量的偏硅酸锂和磷酸锂。六组陶瓷随晶化温度的升高，晶体尺寸逐渐增大。拥有中等晶粒的G3组（0.92±0.14μm）的强度、硬度、弹性模量更高。六组试件中G3组磨损量明显低于其他5组。磨损量最高的是GC-P与GC-O组。G1、G2、G4、GC-P以及GC-O组30万次循环之前为跑合期。60~240万次循环之间为稳定磨损期。G3组在整个磨损循环内磨损量均较小，0~60万次磨损速率小于90~240万次时的磨损速率，故该组60万次循环之前为跑合期。二硅酸锂全瓷冠动态磨损呈现出：“跑合期”、“稳定磨损期”、“剧烈磨损期”。结论：经细化后拥有（0.92±0.14）μm中等长度晶粒的二硅酸锂玻璃陶瓷表现出更高的机械性能和更好的耐磨性能，晶粒尺寸过小或过大的玻璃陶瓷机械性能相对减弱。经过淬火处理后，材料的抗弯强度和硬度都有明显的升高。