基于磨损行为时间特性的二硅酸锂玻璃陶瓷晶体取向调控研究

Because of the excellent biocompatibility and good performance, dental ceramic, especially the glass based ceramic, has been the popular dental material for the tooth defect and dentition defect. But porcelain early fracture and high wear to the opposing tooth due to repeated load cycles are regarded as significant problems. Based on the time-dependent wear behavior of dental ceramic, the biological friction pair of “ceramic restoration-natural tooth” experiences the non-linear wear process during the chewing simulation, which contains running-in, steady and severe wear stages. Literatures and our previous studies show that the porcelain early fracture and high wear to the opposing tooth are related to the wear surface of the running-in stage, and the damage of the wear surface depends on the crystal orientation. Choosing lithium disilicate glass-ceramics as the research object，our research group use equal channel angular pressing through electron backscatter diffraction, oral fatigue wear tester, three-dimensional topography, scanning electron microscope, nanoindenter, to change the crystal orientation of glass-ceramics. The surface morphology, wear resistance and mechanical properties of the ceramics are analyzed. We tend to construct a crystal orientation of the surface of glass-ceramics perpendicular to the direction of chewing force, to improve the mechanical properties and tribological characteristics of lithium disilicate glass-ceramics. We expect to explore a new way for alleviating the wear of “running-in” stage, decreasing the early failure rate of restorations.

齿科瓷修复材料，特别是玻璃基陶瓷材料具有极佳的美学效果及生物相容性，已成为牙体牙列缺损修复主流材料，但修复体的早期失效及对天然牙造成的过度磨耗，仍然是临床面临的主要问题。基于齿科陶瓷材料磨损行为的时间特性，“修复体-天然牙”摩擦副的磨损呈现跑合期、稳定期及剧烈磨损期的非线性动态演变过程。文献报道和我们前期研究表明修复体的早期失效与跑合期的磨面损伤密切相关，而磨面损伤与材料的晶体取向密切相关。本项目以二硅酸锂玻璃陶瓷为研究对象，通过等通道转角挤压等方法，借助电子背散射衍射、口腔疲劳磨损实验机、3D形貌仪、扫描电镜、纳米压入仪等手段，通过改变玻璃陶瓷的晶体取向，并对陶瓷表面微观形貌、磨损性能、力学性能进行分析，以期在玻璃陶瓷表面构建与咀嚼力方向垂直的晶体取向，进而阻碍裂纹扩展，改善其力学性能和摩擦学特性，有效减轻跑合期的磨面损伤，降低修复体的早期失败率，并为优化齿科陶瓷材料提供参考。

经过采用等通道转角挤压的方式压铸陶瓷后，晶体沿平行于挤压方向排列更明显，晶体横向排列，长轴能被完整看到，而在陶瓷横剖面上晶体多成放射状排列。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。可以看出，两组样品具有近乎一致的结晶衍射峰和非晶包。XRD图谱显示两组样品主晶相都为二硅酸锂相，通过晶体对应的衍射峰和玻璃体对应的非晶衍射包可以估算出样品的结晶度。显微组织图像可以看出，二硅酸锂呈典型的棒状形态，形成交叉互锁结构，与退火处理后样品微观形貌没有明显差异，这说明淬火处理不会对玻璃陶瓷样品的微观组织造成影响。每种状态的玻璃陶瓷制备进行三点弯曲测试，进行维氏硬度和断裂韧性测试，退火态和淬火态样品的抗弯强度和硬度测试结果显示，与退火样品相比，经过淬火处理后，材料的抗弯强度和硬度都有明显的升高，体现了淬火处理对LD玻璃陶瓷的强化作用。等通道转角挤压的方式，二硅酸锂玻璃陶瓷的力学性能和耐磨损性能有明显提高；等通道挤压组和常规压铸组二硅酸锂玻璃陶瓷的磨损曲线均可分为“跑合期”和“稳定磨损期”两个阶段；等通道挤压组的“跑合期”较常规压铸组短，磨损速率也更小，磨损量更小。