Fatigue damage analysis of porcelain in all-ceramic crowns / 北京大学学报(医学版)

ABSTRACT

Objective:To investigate the fatigue damage mechanism of porcelain,and its relation with the microscopic defects in clinically failed all-ceramic crowns.Methods: Collecting the bilayered all-ceramic crowns failed in vivo.The fractured surfaces and occlusial surfaces of failed crowns were examined by an optical microscope followed by detailed fractography investigations using a field emission scanning electron microscope.When chemical impurities were of concern,energy-dispersive X-ray spectroscopy analysis was performed to examine chemical composition.A standard practice for fractography failure analysis of advanced ceramics is applied to disclose the fracture mode,and damage character.Results: Three types of fracture features are defined as breakdown of the entire crown,and porcelain chipping-off/delamination.Alumina crowns were usually characterized by breakdown of the entire crown,while zirconia crowns by porcelain chipping-off and delamination.The fatigue damage of porcelain was classified into surface wear,cone crack,and porcelain delamination.The observed microscopic defects in this study included air bubbles and impurity particles.Conclusion: The multi-point occlusial contacts were recommended in all-ceramic restorations clinically.The thickness of porcelain is important for the anti-fatigue ability of porcelain.Cautions have to be taken to avoid contaminations during the veneering processes.