Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany; Department of Biomedical Engineering, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba-cho, Shiwa-gun, Iwate 028-3694, Japan.
Section Medical Materials Science & Technology, University Hospital Tübingen, Osianderstr. 2-8, 72076 Tübingen, Germany.
Dent Mater. 2019 Feb;35(2):270-282. doi: 10.1016/j.dental.2018.11.024. Epub 2018 Dec 3.
The present study investigated the biaxial flexural strengths of bilayered ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/A) disks with various layering porcelains veneered using a slow-cooling protocol.
Five porcelain materials (VITA VM9, Cercon Ceram Kiss, and Vintage ZR with experimental coefficient of thermal expansions; CTEs of 8.45, 9.04, and 9.61ppm/°C) were veneered on Ce-TZP/A disks and slow-cooled after firing to fabricate bilayered specimens (core-to-porcelain thickness: 0.8mm/1.5mm). Biaxial flexural strengths of the specimens with the porcelain layer in tension were tested based on the piston-on-three-ball method (ISO 6872:2008). The data were statistically analyzed using Weibull distribution and Fisher's exact test.
Tensile stresses were observed in the entire porcelain layer while compressive stress at the surface of the Ce-TZP/A layer shifted to tensile stress at the interface between the materials. The cases of small CTE mismatches between the materials showed high Weibull characteristic strengths at the internal and external surfaces of the specimens, except the VM9 group (CTE: 9.0-9.2ppm/°C). The maximum tensile stress was observed on the surface of the porcelain layer, where cracks originated and continuously propagated into the Ce-TZP layer. The Ce-TZP/A fractured into two pieces for large CTE mismatches between the materials, resulting in significantly lower flexural strengths than those fracturing into three pieces for small CTE mismatches.
Flexural strengths and fracture behaviors of bilayered porcelain-Ce-TZP/A disks were influenced by the CTE mismatches, and a small CTE mismatch between the materials was preferred when using a slow-cooling protocol.
本研究调查了采用慢冷却方案的双层氧化铈稳定氧化锆/氧化铝纳米复合材料（Ce-TZP/A）磁盘与各种层压烤瓷的双轴弯曲强度。
将五种烤瓷材料（VITA VM9、Cercon Ceram Kiss 和 Vintage ZR，具有实验热膨胀系数；CTE 分别为 8.45、9.04 和 9.61ppm/°C）涂覆在 Ce-TZP/A 磁盘上，并在烧制后进行慢冷却以制造双层标本（核-瓷厚度：0.8mm/1.5mm）。根据活塞三点球法（ISO 6872:2008）测试具有瓷层拉伸的试件的双轴弯曲强度。使用威布尔分布和 Fisher 精确检验对数据进行统计分析。
在整个瓷层中观察到拉伸应力，而 Ce-TZP/A 层表面的压应力转变为材料界面处的拉伸应力。在材料之间 CTE 不匹配较小的情况下，除了 VM9 组（CTE：9.0-9.2ppm/°C）外，试件内部和外部表面均表现出较高的威布尔特征强度。最大拉伸应力出现在瓷层表面，裂纹由此产生并不断扩展到 Ce-TZP 层。对于材料之间 CTE 不匹配较大的情况，Ce-TZP/A 断裂成两块，导致弯曲强度明显低于 CTE 不匹配较小的情况下断裂成三块的情况。
双层烤瓷-Ce-TZP/A 磁盘的弯曲强度和断裂行为受到 CTE 不匹配的影响，当采用慢冷却方案时，材料之间的 CTE 不匹配较小是优选的。
