Evaluation of bonding effectiveness of a self-etch and an etch-and-rinse adhesive resin to un-treated and Er:Yag laser treated dentin using mini-interfacial fracture toughness test

The aim of current study was to assess interfacial bonding effectiveness of self-etch and etch-and-rinse dental adhesives to untreated and Er:YAG laser-treated dentine using mini-interfacial fracture toughness (mini-iFT) test. 32 selected non-carious third molars were divided into two groups: untreated and Er:YAG laser treated. The laser-treated specimens were subjected to Er:YAG laser with energy density of 25.82 J/cm(2). Both groups were further assigned to two groups based on adhesive systems: self-etch and etch-and-rinse. The teeth were sectioned perpendicular to the adhesive/dentine interface to obtain 1.5 x 2 mm wide longitudinal rectangular sections. A single notch then was prepared at the adhesive-dentine interface. The mini-iFT test was done via a 4-point bend testing until failure and the KIC was calculated. All specimens were observed using a, scanning electron microscope (SEM). The data were analysed using two-way analysis of variance (ANOVA) at a significant level of 0.05. Weibull parameters including Weibull modulus and characteristic strength also were calculated for each experimental group. Two-way ANOVA showed both variables (the type of adhesive system and laser treatment) significantly influenced the mini-iFT values of specimens (p <= 0.001). The self-etch and laser-treated group showed lower mini-iFT than the etch-and-rinse and untreated samples. SEM observations revealed that the fracture region was located at the adhesive-dentine interface in most of the specimens. The Er:YAG laser treatment may adversely affects the bonding effectiveness of the dentine/adhesive interface. The mini-iFT method can be used as a discriminative and valid method for the evaluation of bonding effectiveness at the adhesive-dentine interface.