Interfaces in fixed dental prostheses: Challenges and opportunities

In recent years, zirconia-based restorative systems (i.e., porcelain-veneered zirconia and monolithic zirconia) have emerged as promising materials for all-ceramic prostheses due primarily to their superior mechanical properties, esthetics, and biocompatibility. However, the susceptibility to porcelain fracture as well as the poor fusion and resin-cement bonding capability of zirconia prevent the widespread use of such material systems. We have developed a surface glass infiltration method that creates a functionally graded material layer at the bonding surfaces of zirconia. Our test data show that glass infiltration at the veneering surface can effectively prevent veneer chipping and delamination, whereas that at the cementation surface can increase the interfacial fracture energy of zirconia by over a factor of 3, to a level consistent with feldspathic ceramic. These qualities, together with the increased resistance to flexural and contact damage, edge chipping, and delamination found in previous studies, suggest that functionally graded zirconia can be considered as a viable material option for dental restorations.