Degree of conversion and bond strength of resin cements through different thicknesses of lithium disilicate ceramic using different curing modes

Abstract

Objectives: The aim of this in vitro study was to assess the physical and mechanical properties of resin cements to ceramic substrate using different curing modes by evaluating the degree of conversion and bond strength of these cements. 
 Methods: Hundred twenty square lithium disilicate ceramic discs specimens of three thicknesses (0.5, 1 and 1.5 mm) and 10x10mm diameter were bonded to 120 bovine teeth using two resin cements (one light cure and one dual cure) and using two curing modes (ramp and continuous). As a result, 12 experimental groups were established for bond strength testing. degree of conversion of luting cements was evaluated using Fourier transform infrared spectroscopy (FTIR).
 Results: using the continuous mode compared to the ramp after controlling the type of resin and material thickness showed no significant difference(P>0.001) in SBS and DC. the effect of changing the material thickness between 0.5mm, 1mm and 1.5mm after controlling the resin type and mode of light curing, showed significant difference (p<0.001) from 1mm to 1.5mm using light-cured resin and continuous curing mode for SBS. while for the DC these correlations between different material thicknesses and both light cure type of resin and continuous light-curing mode was significant (p<0.001), it was also significant with dual cure cement. This study also evaluated the effect of using dual-cured resin cement compared to the light-cured resin cement on the SBS and DC, for the SBS the effect was significant with higher thicknesses (p<0.001 for the thickness of 1.5 mm) but not significant with thicknesses less than this such as 0.5mm and 1mm (P>0.05).
 Conclusion: There is no change on the effect of changing light curing mode on the DC and SBS increasing the thickness decrease SBS and DC, dual-cured resin performed better when used for thickness of 1.5mm.