Bond strength and interfacial stability of a universal adhesive to alendronate-treated dentin

The enzymatic degradation of the hybrid layer by endogenous matrix metalloproteinases (MMPs) represents the major cause of resin-dentin bond strength deterioration. The current study assessed the influence of dentin pre-bonding treatment with alendronate, an MMP inhibitor, on the efficacy of a universal adhesive.Ninety-six extracted molars were randomly allocated into four groups (n = 24) based on dentin surface treatment: no treatment (control), 2 wt% chlorhexidine, 0.03 wt% alendronate, and 0.3 wt% alendronate. Each group was further classified into two sub-divisions (n = 12) according to the adhesive application mode: etch-and-rinse (ER) and self-etch (SE). On flat dentin surfaces, the treatment solution was applied, followed by application of universal adhesive (All Bond UNIVERSAL, BISCO) and composite buildup. Eighty teeth were used for the assessment of microtensile bond strength (µTBS), failure mode, and nanoleakage, while the remaining sixteen teeth were examined using scanning electron microscopy (SEM) to assess the bonded interface. All tests were conducted at 2 time intervals; after 24 h and after aging for 5000 thermocycles. Statistical analysis of the µTBS data was performed using three-way ANOVA followed by Tukey's post hoc test. The 0.3 wt% alendronate-treated ER group exhibited the highest µTBS values under both immediate and aged conditions (p value < 0.05). Using SE adhesive mode, the same treatment showed relatively higher µTBS values; however, the variations among SE groups were not significant. Failure mode analysis revealed that immediate alendronate-treated ER groups predominantly exhibited cohesive failures, whereas the ER control group presented a higher frequency of mixed failures. Following thermocycling, alendronate-treated ER groups showed a shift toward mixed failure mode. Nanoleakage analysis indicated greater silver uptake in the ER groups compared to SE groups, particularly after aging. Micromorphological surface analysis by SEM showed that the 0.3 wt% alendronate-treated ER group exhibited the most pronounced resin penetration. It has been concluded that dentin treatment with alendronate specifically 0.3 wt%, before bonding, appeared to enhance bond strength, particularly with etch-and-rinse mode. The results of failure mode analysis, nanoleakage evaluation and micromorphological interface observations confirmed these findings.