Veneered zirconia chipping: experimental and FEA study

Abstract

Due to the high incidence of chipping on veneered Yttria Tetragonal Zirconia Polycrystal (Y-TZP), authors began to use the edge chipping test to evaluate dental ceramics, checking the influence of framework materials (metal or zirconia) in the failure of veneering porcelain. However the test showed to be inefficient, probably because the bar format specimen does not reproduce thermal stresses pattern of a prosthetic crown. Therefore, a recent study included crown format specimens to evaluate the chipping resistance an experimental zirconia. The objective of this project is to verify if the chipping test on crown specimens is a good predictor of porcelain chipping on veneered Y-TZP. Specimens will be made in bar and crown geometry, with thicknesses of porcelain (ep) and framework (ei) offering two ratio values of ep/ ei (0.25 and 0.5). The specimens will be submitted to two cooling protocols (slow and fast) that certainly offer different results of chipping resistance on the veneering porcelain, by differences in the distribution of residual thermal stresses. 3D finite element models will be developed for each experimental situation, taking into account the thermal stresses generated during cooling protocol. The chipping failure will be simulate using extended finite element method (X-FEM). The test will be considered a good predictor of porcelain chipping resistance on bilayers specimens if it shows significant differences between zirconia and metal framework and between slow and fast cooling protocol. At the end, we intend to have further information to understand the mechanism of this type of failure and propose ways to avoid it. (AU)