Micro-tensile bond testing of resin cements to dentin and an indirect resin composite

Objectives: Micro-tensile bond strength (μTBS) evaluation and fractographic analysis were used to compare four resin cement systems (AC: All-Bond 2/Choice; RX: Single Bond/RelyX ARC; SB: Super-Bond C&B; and PF: Panavia F) in indirect composite/dentin adhesive joints. Methods: Flat dentin surfaces were created on extracted human third molars. The resin cements were used according to the manufacturersʹ instructions for bonding silanized composite overlays to deep coronal dentin. 0.9×0.9 composite–dentin beams prepared from the luted specimens were stressed to failure in tension. Dentin sides of all fractured specimens were examined by scanning electron microscopy (SEM) to examine the failure modes. In group PF, morphologic features that could not be resolved at the SEM level were further validated by transmission electron microscopy (TEM) examination of the SEM specimens. Results: Statistical analyses revealed significant difference (p<0.05) among μTBS and failure modes in the resin cement groups. The two groups (AC and RX) with highest μTBS failed predominantly along the composite overlay/cement interface. Cohesive failure in resin cement was primarily observed in group SB that exhibited intermediate μTBS values. In group PF with the lowest μTBS, failure occurred mostly along the dentin surface. Globular resin agglomerates seen by SEM on PF-treated dentin were distinguished from silica fillers by TEM. Significance: The bond between the processed composite and the luting resin cement was the weak link in indirect composite restorations cemented with AC or RX. Super-Bond C&B exhibited intermediate tensile strength and Panavia F is less reliable when used in conjunction with a self-etching primer for bonding indirect restorations to dentin.