Marginal Fit and Shear Bond Strength of IPS-Emax to Zirconia

The development of yttrium oxide partially stabilized zirconia (Y-TZP) has allowed the use of ceramic in the anterior zone combined with load-bearing sites. In order to achieve natural esthetics, a compatible thermal coefficient feldespathic ceramic is fired on top of the zirconia cores. However, delamination of the veneering ceramic is the primary cause of failure of this type of restorations. Objectives: To compare the marginal fit and to measure the shear bond strength between one veneering ceramic to four different zirconia cores. Methods: The four systems tested were Zirkonzahn®(ZkZ), Lava®(L;3M), Cercon®(C,Dentsply) and Zircad® (Zc;Ivoclar). Five cores of each system (n=20) were maded and placed in the metal master die to measure the marginal fit with an electromicroscope in four zones (mesial, distal, lingual and buccal). After firing the veneering feldespathic ceramic (IPS E-max, Ivoclar) on top of the cores, the samples were subjected to shear force in a Instrom universal testing machine. Then the broken samples were examined with a stereomicroscope to determine the type of fracture. Data was analyzed using ANOVA. Results: The four systems showed similar marginal fit: C:44.708µm, Zc:53.161µm; L:53.678µm y Zkz:70.102µm. The shear bond strength was Zc:8.7MPa, L:8.2MPa, Zkz:6.8MPa and C:5.6Mpa. The microscopic observation revealed 100% adhesive type of fracture. Conclusion: No significant statistical difference was found between the marginal fit of the four systems (p:0,286) or the shear bond strength of the veneering ceramic (p:0,313). The marginal fit found in all the systems is acceptable for a favorable clinical prognosis. The interface zone ceramic-zirconia cores is very weak so these systems must be used carefully.