Lecturer, Department of Prosthodontics, Gazi University, Ankara, Turkey.
Associate Professor, Department of Prosthodontics, Gazi University, Ankara, Turkey.
J Prosthet Dent. 2018 Mar;119(3):473-480. doi: 10.1016/j.prosdent.2017.05.003. Epub 2017 Jun 20.
The demand for ceramic restorations has increased over the past years, and now various machinable materials can be used for chairside computer-aided design and computer aided manufacturing (CAD-CAM) systems. Limited studies of these new materials make it difficult to evaluate their mechanical performance, advantages, and limitations.
The purpose of this in vitro study was to investigate the fracture resistance of CAD-CAM monolithic ceramic and veneered zirconia molar crowns after thermomechanical aging.
A mandibular first molar tooth was prepared, and 12 different experimental groups were generated (n=10). An aging procedure was performed by subjecting the specimens to 12×10 mechanical cycles and 5000 thermocycles. Survival analysis was performed according to the thermomechanical aging. The fracture resistance (load at fracture) of all specimens was evaluated with 1-way analysis of variance after the means had been compared using the Tukey honest significant difference test and Weibull distributions of the experimental groups (α=.05).
According to the results, the differences between the fracture resistance of the groups were found to be significant. Restorations in the dual network ceramic crown group fractured catastrophically during thermomechanical aging. In all groups, the highest value was found for monolithic zirconia, followed by monolithic lithium disilicate crowns (P<.05). Both of the monolithic crowns made of lithium disilicate derivates and zirconia crowns veneered with lithium disilicate ceramic showed no differences from each other (P>.05). The Weibull modulus (m) ranged from 4.22 to 8.58, and conventionally veneered and overpressed zirconia showed the lowest Weibull modulus values among the tested groups, indicating greater variation of the data.
The highest fracture resistance was observed for yttria-stabilized zirconia crowns, followed by lithium disilicate derivates. Veneered zirconia restorations generally showed lower resistance than these ceramics. The dual network ceramic crowns fractured during thermomechanical aging.
近年来，对陶瓷修复体的需求有所增加，现在可以使用各种可加工材料来进行椅旁计算机辅助设计和计算机辅助制造（CAD-CAM）系统。这些新材料的研究有限，使得评估它们的机械性能、优势和局限性变得困难。
本体外研究的目的是调查热机械老化后 CAD-CAM 整体陶瓷和贴面氧化锆磨牙冠的断裂阻力。
预备下颌第一磨牙，并生成 12 个不同的实验组（n=10）。通过对试件进行 12×10 次机械循环和 5000 次热循环来进行老化程序。根据热机械老化进行生存分析。使用 Tukey 诚实显著差异检验和实验组的威布尔分布（α=.05）比较平均值后，使用单向方差分析评估所有试件的断裂阻力（断裂时的载荷）。
根据结果，发现各组之间的断裂阻力存在显著差异。在热机械老化过程中，双网络陶瓷冠组的修复体发生灾难性断裂。在所有组中，整体氧化锆的断裂阻力最高，其次是整体锂硅玻璃陶瓷冠（P<.05）。用锂硅玻璃衍生材料制成的两种整体冠和用锂硅玻璃陶瓷贴面的整体氧化锆冠彼此之间没有差异（P>.05）。威布尔模数（m）范围为 4.22 至 8.58，传统贴面和过压氧化锆的威布尔模数值在测试组中最低，表明数据的变化较大。
氧化锆的断裂阻力最高，其次是锂硅玻璃衍生材料。贴面氧化锆修复体的阻力一般低于这些陶瓷。双网络陶瓷冠在热机械老化过程中发生断裂。
