Bond strength and monomer conversion of indirect composite resin restorations, Part 1: Light vs heat polymerization.

Abstract

To assess the resin microtensile bond strength (MTBS) and the monomer conversion (MC) of indirect composite resin restorations made of three different materials. Two light-polymerized direct materials (Filtek Z100 and Premise) and one light- and heat-polymerized indirect material (Premise Indirect) were used. For MTBS testing, 42 cylindrical samples were fabricated (7 pairs per material). Surface conditioning included airborne-particle abrasion, cleaning, and application of a silane. Cylinders were bonded to each other using adhesive resin (Optibond FL). Specimens were stored in water for 24 h. Another 15 cylinders (5 per material) were fabricated for MC measurements (FT-IR) immediately and at 24 h. The MTBS data were submitted to one-way ANOVA and the MC to two-way ANOVA (material and storage time) (α=0.05), followed by post-hoc comparisons with the Tukey test. The MTBS to Z100 was 72.2 MPa, significantly higher than that to Premise (48.4 MPa) and Premise Indirect (52.7 MPa). The immediate MC was similar for all materials (range 51% to 56%) and significantly increased at 24 h (range 57% to 66%), except for Z100. Premise Indirect showed the highest MC (66% at 24 h). Z100 showed better "bondability" than Premise and Premise Indirect. Premise Indirect, with its heat initiator, did not present a higher MC.