Preheated composite resins versus luting cement: Degree of conversion, film thickness, color stability and bond strength to enamel and ceramic veneers

Purpose The literature is scarce regarding the use of preheated composite resin for cementing dental ceramic veneers. The purpose of this study is to evaluate the effect of using preheated composite resins as cementing agents on the degree of conversion, film thickness, color stability and bond strength of dental ceramic veneers. Material and methods Three composite resins, Filtek Z100 (Z100), Opus Bulk Fill APS (Opus) and Viscalor Bulk (Viscalor) were preheated and compared with Opus Bulk Fill Flow APS (Opus Flow) and resin cement RelyX Veneer (RelyX). The properties of degree of conversion, film thickness, color stability and microshear bond strength were tested. Statistical analysis was performed using ANOVA and Holm-Sidak tests (α = 0.05). Results The Opus Flow showed a higher degree of conversion compared to Z100 and Viscalor ( P < 0.05), but similar to Opus and RelyX. The film thickness of all preheated resins was greater than the film thickness of the flow resin and the resin cement ( P < 0.001). In the enamel surface, the bond strength of Viscalor was superior to RelyX ( P < 0.001). In the ceramic surface, the bond strength of preheated resins was superior to the resin cement ( P < 0.05). Color stability was significantly influenced by the time factor ( P < 0.05), but there was no difference between the different materials ( P > 0.05). There was no difference between the storage time of 30 days and 6 months. Conclusions The preheated composite resins showed a degree of conversion and color stability similar to the resin cement, but its film thickness was greater than the resin cement and the flowable resin. Viscalor showed the highest bond strength to enamel. Clinical implications Although preheated resins present similar characteristics to resin cements and flowable composite resins, the film thickness of preheated composite resins is high, which can lead to failures in the adaptation of dental ceramic veneers or even the fracture of the dental ceramic veneer during its cementation.