Degree of conversion of dual-cure luting resins light-polymerized through various materials

Abstract

Objective. The aim of this study was to investigate the degree of monomer conversion of four dual-cure luting resins irradiated through various restorative materials or dentin. Material and methods. RelyX ARC (3M-ESPE), RelyX Unicem (3M-ESPE), Variolink 2 (Ivoclar,Vivadent), and Panavia F 2.0 (Kuraray) were mixed in accordance with the manufacturer's instructions. They were placed under the disks (thickness 1.5 mm) representing a metal restoration, a composite restoration (Sinfony D A3), a fiber-reinforced composite (EverStick 0.5 mm + 1.0 mm Sinfony D A3) restoration, and dentin. Five specimens (thickness 0.6 mm) in each group were irradiated through the disks for 40 s (Optilux-501, 800 mW/cm²). Light polymerization of the dual-cure luting resin without the covering disk was used as control. The degree of monomer conversion (DC%) was determined by Fourier transform infrared spectroscopy (FT-IR)/ATR spectrometry from the bottom of the resin. The infrared spectra were recorded at every 5.2 s for 15 min beginning from the mixing of the resin. Results. ANOVA revealed significant differences in DC% between the luting resins tested (p<0.001) and the different restorations (p<0.001). RelyX ARC showed the highest degree of conversion 15 min after the start of polymerization, whereas Panavia F 2.0 and RelyX Unicem showed the lowest. Conclusions. The degree of conversion of dual-cured luting resins differed significantly. Furthermore, the restorative material significantly influenced the DC% of the dual-cure luting resin underneath.