Evaluation of the flexural resistance and stress contraction of a silorane-based composite submitted to different protocols of polymerization

Abstract

When introduced to the market, silorane-based materials promised less contraction compared to other materials. The purpose of this study was to evaluate the contraction stress, flexural strength, and elastic modulus of the Filtek Silorane composite with different photoactivation protocols. Filtek Silorane and Filtek Z350 composites were inserted in a circular photoelastic resin matrix and subjected to photoactivation at 650 mW cm2 for 40 s (protocol I), 325 mW cm2 for 80 s (protocol II), 100 mW cm2 for 260 s (protocol III), 100 mW cm2 for 5 s + 1 min delay +650 mW cm2 for 39.5 s (protocol IV), or 100 mW cm2 for 5 s + 3 min delay +650 mW cm2 for 39.5 s (protocol V). Five samples were prepared for each resin with each photoactivation protocol. To determine contraction stress, fringes were analyzed in a polariscope. For flexural strength analyses, 25 specimens (10 × 2 × 2 mm) of each resin with each photoactivation protocol were submitted to the 3-point bending test in a universal testing machine. Data were submitted to ANOVA and post hoc Tukey’s tests (α = 0.05). Filtek Silorane showed higher contraction stress results than Filtek Z350 for protocols II (16.4 ± 3.88 vs. 5.9 ± 1.64 MPa), IV (17 ± 2.67 vs. 8.8 ± 1.30 MPa), and V (16.3 ± 3.33 vs. 5.1 ± 1.95 MPa). Both resins showed similar flexural strength values, but the elastic modulus of Filtek Silorane was significantly higher with all photoactivation protocols. Pulse-delay photoactivation was effective for Filtek Z350, but not Filtek Silorane, because the elastic modulus and contraction stress were reduced for Filtek Z350 without any change in flexural strength.