Previous work has shown that sputter-deposited thin-film coatings can improve the fracture strength of dental ceramics. A key consideration of this type of modification is to enhance fracture resistance without compromising any existing advantageous ceramic features. To have practical value, the thin-films should not cause any reduction in bond strength with traditional luting cements, or compromise the esthetics. Alumina, a relatively tough ceramic, with suitable esthetic properties, is one potential thin-film coating material. Objectives: The purpose of this study was to investigate the effect of sputter deposited thin-film alumina coatings on the shear bond strength between modified dental ceramic and composite, joined using standard ceramic bonding procedures. Methods: Twenty plates (10x12x5mm, Dicor MGC) were ground through 600-grit SiC abrasive and etched with ammonium bifluoride. Ten plates were coated on the prepared surface with a 5mm thick alumina film (99.99% alumina) using RF-magnetron sputtering. Un-coated plate surfaces were treated with silane (RelyX Ceramic Primer, 3M). Resin adhesive (Single Bond, 3M) was then applied to the surface of all plates, followed by application of a dental composite (Z100, 3M) to all specimens in gelatin capsules (diameter=4.5mm). Specimens were stored in DI-water for 168h at 37°C. The shear bond strength of each specimen was measured in an Instron (Model 4411) at a crosshead speed of 0.5mm/min. Results were analyzed by ANOVA (p≤0.05). Results: Mean shear bond strengths were: No coating, 12.2 ± 1.3 MPa; 5mm alumina coating, 13.5 ± 1.9 MPa. There was not a statistically significant difference between the mean shear bond strengths of the two groups. Conclusion: The results of this study indicate that application of a sputter-deposited alumina thin-film does not adversely affect the bond strength of a dental ceramic with a traditional ceramic bonding system. This work was supported by NIH 5R01DE013511-02.

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