Comparison of the microshear bond strength of feldspathic porcelain to enamel with three luting resins

Abstract

The purpose of this study was to compare microshear bond strength of three different luting resins using a new microshear method closely simulating clinical condition. Thirty 1-mm-thick slices of intact human first molars and thirty 0.8-mm-diameter feldspathic porcelain rods were etched by 37% phosphoric acid for enamels and 9.5% hydrofluoric acid for porcelains. Adhesive (Margin bond) was applied on both silaned porcelain and enamel surfaces. Three luting agents were used as follows: (1) dual polymerized cement (DP) (Variolink II refill), (2) light polymerized cement (LP) (Variolink II base), and (3) flow composite (FC) (Tetrick flow). Porcelain rods were attached to flat enamel surfaces followed by cementation. The specimens were thermal cycled for 500 cycles between 5 and 55°C, and microshear test was then performed with wire and loop method using Dillon Quantrol. Modes of failure were identified by stereomicroscope, and one sample of each group was observed with SEM. finally collected data were statistically analyzed using one-way ANOVA (P<.05). The mean microshear bond strengths were 21.48 (DP), 23.92 (LP) and 24.57 (FC) in MPa units. Most cohesive failures occurred in groups LP and FC, whereas most adhesive failures were observed in group DP. Bond strength of feldspathic porcelain to enamel with studied luting resins were not significantly different among the groups based on current method (P<.05).