Characterization of Residual Stresses in Veneering Ceramics for Prostheses with Zirconia Framework

Abstract The aim of this study was to evaluate the influence of the coefficient of thermal expansion (CTE or α) and glass transition temperature (Tg) of three veneering ceramics used with zirconia frameworks of full-arch fixed prostheses. The generation of residual stresses and linear contraction after the simulation of the cooling process and mechanical loading were measured. The analysis was based on the finite element method in three-dimensional model of a maxillary full-arch fixed prosthesis with zirconia framework (e.max ZirCAD) and veneer by felsdpathic ceramics (GEC - IPS e.max Ceram, GVM - Vita VM9 and GLC - Lava Ceram). The linear contraction simulation was performed by cooling the structures from the Tg of each veneer ceramic at room temperature (25°C). A loading of 100 N on the occlusal region of the first molar was performed. The magnitude of the maximum principal stress (smax) and linear contraction were evaluated. The levels of CTE mismatch between veneering ceramics and framework showed no relevant influence on smax and linear contraction. The Tg values of the veneer ceramic showed to be directly proportional to amount of smax and linear contraction. The GEC presented the highest values of smax and linear contraction. The GVM and GLC did not present significant differences between them. In conclusion, GVM was similar to GLC, while GEC presented differences in relation to other veneer ceramics in terms of residual stress and linear contraction.

摘要 本研究旨在评估用于全牙弓固定修复体氧化锆支架的三种饰面陶瓷的热膨胀系数（coefficient of thermal expansion，简称CTE或α）与玻璃化转变温度（glass transition temperature，简称Tg）对其产生的影响。本研究测量了冷却过程模拟与机械载荷作用后产生的残余应力与线性收缩量。本分析采用有限元法（finite element method），以上颌全牙弓固定修复体的三维模型为研究对象，该修复体以e.max ZirCAD作为氧化锆支架，并分别采用三种长石质饰面陶瓷进行饰面：GEC - IPS e.max Ceram、GVM - Vita VM9及GLC - Lava Ceram。线性收缩模拟通过将各饰面陶瓷从其自身玻璃化转变温度冷却至室温（25℃）完成。随后在第一磨牙的咬合区域施加100N的载荷。研究评估了最大主应力（smax）与线性收缩量的大小。结果显示，饰面陶瓷与支架间的热膨胀系数失配程度对最大主应力与线性收缩量未产生显著影响；饰面陶瓷的玻璃化转变温度则与最大主应力及线性收缩量呈正相关。其中GEC的最大主应力与线性收缩量数值最高，GVM与GLC之间未呈现显著差异。综上，GVM与GLC表现相近，而GEC在残余应力与线性收缩方面与其余两种饰面陶瓷存在显著差异。