Can cement film thickness influence bond strength and fracture resistance of fiber reinforced composite posts?

Abstract

This study compared the influence of cement film thickness (CFT) on bond strength (BS) and fracture resistance (FR) of fiber-reinforced composite (FRC) posts to root canal. One hundred bovine incisors were used for BS and FR analysis (n = 10) and distributed into five experimental groups according to FRC post diameters (WhitePost DC no. 0.5, no. 1, no. 2, no. 3, no. 4), leading to five different CFTs. The canals were prepared using drill no. 4 provided by the post manufacturer and irrigated with 2.5% NaOCl. After conditioning (24% H2O2/5 min) and silanization, posts were cemented with resin cement. BS was evaluated using push-out test and FR using the compression test at 45°. A stereomicroscope was used to measure CFT and to analyze failure pattern. BS data were subjected to two-way ANOVA and Scheffé test for contrast (α = 0.05); FR data were subjected to one-way ANOVA. BS was significantly affected by CFT, as the most well-adapted post achieved the highest values (p < 0.05). BS was similar for all root thirds. CFT did not affect fracture resistance. No root fractures were observed. A FRC post well adapted to the root canal results in higher BS values. Different CFTs did not influence the FR of teeth restored with FRC posts. The results indicate that post retention is improved when a well-adapted post is used, although this has not been critical to fracture resistance.