Contact deformation and cracking of zirconia/cement/foundation dental multilayers

The paper presents the results of combined experimental, analytical and computational studies of contact-induced deformation and cracking in zirconia/cement/foundation dental multilayers, where cement and foundation layers are commercially used dental adhesive and restoratives. Hertzian contact tests were performed on the multilayers. A novel technique, dual-beam focused ion beam and scanning electron microscopy (FIB/SEM) was used to examine the crack/microstructure interactions in the dental multilayer structures. The FIB/SEM images show sub-surface inter/intragranular cracking modes that have not been reported before. The critical loads corresponding to onset of sub-surface radial cracking were found to exhibit a strong dependence on the monotonic loading rates. A rate-dependent environmentally assisted slow crack growth (RDEASGG) model was used to predict the loading rate dependence of the critical loads. The implications of the results are discussed for the design of durable dental multilayers.