Effects of Treatment and Storage Conditions on Ceramic/Composite Bond Strength

During the past few years, the interest in using ceramic inlays and veneers has increased. New materials and methods have been introduced to bond these restorations to resinous materials. Since our knowledge of how to optimize such bonding is limited, the objective of this study was to test the hypothesis that various surface treatment variables and combinations of these variables affect the strength of the ceramic/composite interphase of ceramic inlays differently. The influences of material composition, surface-roughening method, silane treatment, silane heat treatment, and storage condition on bond strength were investigated. Three ceramics (Dicor®, Mirage®, Vitabloc®), three surface-roughening methods (etching, sandblasting, grinding), three silane treatments (γ-methacryloxypropyltrimethoxysilane [MPS], MPS + paratoluidine, vinyltrichlorosilane), two heat treatments (20°C for 60 s, 100°C for 60 s), and two storage conditions (24-hour dry, one yr in water at 37°C) were studied. For each of the 108 combinations, five specimens were tested. Ceramic cylinders were treated according to group assignment and bonded to blocks of the same ceramic material with a dual-cured resin. The shear bond strength was determined, and the experimental factors were evaluated by analysis of variance. The results showed that surface-roughening method had the strongest effect on bond strength, while ceramic selection had the least significant effect. Of the surface-roughening methods, etching was associated with higher bond strength values than either sandblasting or grinding. Bond strength to etched ceramics remained constant after water storage, while the bond strength to both sandblasted and ground specimens decreased by from 50 to 75% compared with dry storage. Heating the MPS-coated specimens to 100°C resulted in bond strength twice as high than if no heating was used. Mechanical interlocking appears to be the key factor influencing the ceramic-composite bond strength.