Bonding of Composite Resin Luting Cement to Fiber-reinforced Composite Root Canal Posts

The aim of this study was to compare bonding of composite resin luting cement to a fiber-reinforced composite (FRC) root canal post with either a cross-linked or a semi-interpenetrating polymer network (IPN) polymer matrix. Four different types of prefabricated FRC posts with a cross-linked polymer matrix and two types of FRC posts with a semi-IPN polymer matrix which were individually formed were tested. Serrated titanium posts served as the reference. An auto-polymerizing resin luting cement was used for cementing the posts into the holes of composite resin disks. The pull-out force was measured using a universal testing machine after the post/cement/disk system had been stored dry or thermocycled (5°C/55°C, 6000x) in water. The bonding sites of the posts were examined with SEM. The FRC posts with a semi-IPN polymer matrix gave significantly higher pull-out force values than the prefabricated FRC posts with a smooth surface and a cross-linked polymer matrix (p 0.004). The highest pull-out force was obtained with serrated titanium posts. Both the type of FRC post and thermocycling had a significant effect on the pull-out force (n = 8, ANOVA p 0.001 and p 0.007, respectively). SEM photomicrographs confirmed the results. This study showed that FRC posts with a semi-IPN polymer matrix bonded better to composite resin luting cement than did prefabricated FRC posts with a cross-linked polymer matrix, although their pull-out force was not as high as that of the mechanically interlocked serrated titanium posts. Keywords: root canal posts, fiber reinforced composite, fiber reinforced composite root canal posts, pull-out force, SEM