Bond strength of a composite luting agent to alumina ceramic surfaces

OBJECTIVE: The purpose of this study was to evaluate the shear bond strength (SBS) of a dental luting agent to alumina ceramics after different surface pretreatment. MATERIAL AND METHODS: Specimens (n=50) of pressed blocks (10 x 0 x 5 mm) of alumina ceramic (Procera AllCeram) were divided into untreated specimens (AF) as provided by the manufacturer and polished specimens (AP). Five groups of specimens (n=5 x 10) with different surface pretreatments were prepared. Groups 1 and 2: AF and AP without any pretreatment; Group 3: AF treated with silane, (AF-s); Group 4: AF treated with RF plasma spray (AF-RF); Group 5: AF treated with low fusing porcelain (AF-p) glass pearls. Composite cylinders (5 x 5 mm) were cemented to the test specimens with a resin luting agent. The specimens were loaded to failure in shear mode using a universal testing machine. Recorded loads were used to calculate SBS in MPa. The results were analyzed using one-way ANOVA and the Tukey HSD multiple comparison test at alpha = 0.05. Scanning electron microscopic micrographs (SEM) were used to characterize surfaces of interest. RESULTS: Polished surfaces had significantly lower SBS (p < 0.05) compared with untreated specimens (AP vs AF). Silanated, non-polished surfaces (AF-s) revealed lower SBS, even though the result was not significantly different from that of AF-s without silane treatment. Plasma treatment improved SBS by a factor of 2 (p<0.05) and treatment with low-fusing porcelain micro pearls increased SBS by a factor of 3 compared to untreated surfaces (p<0.05). The layer of glass pearls did not exceed 5 microm (SEM). CONCLUSIONS: Within the limitation of the conditions of this study, treatment of alumina oxide ceramic surfaces with a plasma spray coating or a low-fusing porcelain pearl layer significantly increased the SBS of a resin luting agent to the ceramic surface.