Fabris Douglas, Souza Júlio C M, Silva Filipe S, Fredel Márcio, Mesquita-Guimarães Joana, Zhang Yu, Henriques Bruno
Ceramic and Composite Materials Research Group (CERMAT), Federal University of Santa Catarina (UFSC), Campus Trindade, Florianópolis/SC, Brazil.
CMEMS-UMinho, University of Minho, Campus de Azurém, 4800-058 Guimarães, Portugal; School of Dentistry (DODT), Post-Graduation Program in Dentistry (PPGO), Federal University of Santa Catarina, Campus Trindade, 88040-900, Florianópolis/SC, Brazil.
Ceram Int. 2017 Mar;43(4):3670-3678. doi: 10.1016/j.ceramint.2016.11.209. Epub 2016 Dec 1.
Layered ceramic systems are usually hit by residual thermal stresses created during cooling from high processing temperature. The purpose of this study was to determine the thermal residual stresses at different ceramic multi-layered systems and evaluate their influence on the bending stress distribution. Finite elements method was used to evaluate the residual stresses in zirconia-porcelain and alumina-porcelain multi-layered discs and to simulate the 'piston-on-ring' test. Temperature-dependent material properties were used. Three different multi-layered designs were simulated: a conventional bilayered design; a trilayered design, with an intermediate composite layer with constant composition; and a graded design, with an intermediate layer with gradation of properties. Parameters such as the interlayer thickness and composition profiles were varied in the study. Alumina-porcelain discs present smaller residual stress than the zirconia-porcelain discs, regardless of the type of design. The homogeneous interlayer can yield a reduction of ~40% in thermal stress relative to bilayered systems. Thinner interlayers favoured the formation of lower thermal stresses. The graded discs showed the lowest thermal stresses for a gradation profile given by power law function with p=2. The bending stresses were significantly affected by the thermal stresses in the discs. The risk of failure for all-ceramic dental restorative systems can be significantly reduced by using trilayered systems (homogenous or graded interlayer) with the proper design.
层状陶瓷系统通常会受到从高温加工温度冷却过程中产生的残余热应力的影响。本研究的目的是确定不同陶瓷多层系统中的热残余应力，并评估它们对弯曲应力分布的影响。采用有限元法评估氧化锆 - 瓷和氧化铝 - 瓷多层圆盘的残余应力，并模拟“活塞 - 环”试验。使用了随温度变化的材料特性。模拟了三种不同的多层设计：传统的双层设计；三层设计，中间有一层成分恒定的复合层；以及梯度设计，中间层具有性能梯度。研究中改变了诸如层间厚度和成分分布等参数。无论设计类型如何，氧化铝 - 瓷圆盘的残余应力都比氧化锆 - 瓷圆盘小。相对于双层系统，均匀的中间层可使热应力降低约40%。较薄的中间层有利于形成较低的热应力。对于由幂律函数p = 2给出的梯度分布，梯度圆盘显示出最低的热应力。圆盘内的热应力对弯曲应力有显著影响。通过使用设计合理的三层系统（均匀或梯度中间层），可以显著降低全瓷牙修复系统的失败风险。
