Influence of universal adhesive system application strategies on the long-term bond strength to dentin of CAD-CAM restorative materials

Abstract

The objective of this study was to evaluate the influence of dentin application strategies of the universal adhesive system (Scotchbond Universal 3 M/ESPE) on the bond strength of a lithium disilicate-based ceramic and a nanoceramic resin, using the microshear test. A total of 40 healthy third molars were sectioned to expose flat occlusal medium dentin, and separated into four groups (n = 10). The molars were selected according to dentin treatments (application or nonapplication of phosphoric acid prior to universal Scotchbond Universal adhesive), and to the indirect materials obtained by CAD-CAM (lithium disilicate ceramics – IPS e.max CAD, and nanoceramic resin – Lava Ultimate), under study. Ceramic sticks of lithium disilicate and nanoceramic resin measuring 1 mm2 were cemented with Rely XTM Ultimate resin cement on the dentin surface, and stored in distilled water for 48 h or 12 months at 37 °C. The microshear test was performed using a universal testing machine, at a speed of 0.5 mm/min. The values were recorded in MPa, and submitted to three-way ANOVA with a significance level of 5%. The results indicated that the interactions among restorative material, dentin treatment and timepoint was not significant (p = 0.841). However, the 12-month storage time significantly affected the bond strength (p = 0.016) of all the groups. It was concluded that bond strength to dentin decreased over time, regardless of the mode of application of the universal adhesive system or the type of restorative material.