Influence of polymerization mode on flexural properties of esthetic resin luting agents

Abstract

Dual-polymerized esthetic resin luting agents have become popular. However, it is not clear whether the autopolymerized versions of such products have adequate strength to meet clinical requirements. The aim of this study was to investigate the effect of different polymerization modes on the flexural properties of esthetic resin luting agents. Ten esthetic resin luting agents were studied. Materials with 3 polymerization modes (dual, auto, and light) were Appeal, Calibra, Illusion, Lute-It, and Variolink-II; those with 2 polymerization modes (dual and auto) were Bistite-II-DC, Cement-It-C&B, Clearfil-DC-Cement, Linkmax, and Nexus2-Dual-Syringe. Five flexural strength specimens (2 x 2 x 25 mm) were made for every available polymerization mode for each material. The specimens were stored in distilled water for 24 hours at 37 degrees C. The specimens were then tested for flexural strength (MPa) and flexural modulus (GPa) using the 3-point bending method on a universal material testing machine at a cross-head speed of 0.5 mm/min. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests (alpha=.05). Flexural strength values were the highest for dual-polymerized Nexus2-Dual-Syringe (155 MPa), whereas the values were lowest for autopolymerized Bistite-II-DC (56 MPa) and light-polymerized Appeal (63 MPa). Flexural moduli values ranged from 4.3 to 10.0 GPa. The polymerization mode and luting agent influenced flexural strength and modulus significantly (P<.05). Dual-polymerized resin luting agents had higher or equal flexural strength compared to the autopolymerized mode. All the groups tested passed the flexural strength requirement of the ISO 4049 specification.