Long-term adhesive interface stability and ultra-structural properties by phosphosilicate-based bioactive glass primer

Phosphosilicate-based bioactive glasses (BGs) are promising remineralization materials due to their bioactivity, which could enhance the dentin adhesive interface. This study aimed to evaluate the immediate and 12-month effects of a BG-containing primer (BG-primer) on the biomechanical and ultrastructural properties of dentin bonding using two adhesive strategies. Experimental groups (n = 5) applied BG-primer before either an etch-and-rinse (ER) or self-etch (SE) adhesive strategy on third molar dentin, while controls used ER/SE without BG-primer. Specimens were subjected to micro-tensile bond strength (µTBS) testing immediately and after 12 months. Data were analyzed using two-way ANOVA and Tukey's test (α = 0.05). SEM was used to evaluate nanoleakage (NL) and BG-primer localization, while ATR-FTIR spectroscopy analyzed BG in dry conditions, immediate hydration, and after six hours. BG-primer significantly increased µTBS at 12 months (p < 0.05) without affecting NL. BG particles colocalized near the hybrid layer, maintaining its structural integrity. ATR-FTIR revealed hydration-induced modifications in BG, persisting after six hours. The BG-primer improved long-term adhesive performance in SE systems and stabilized the ER interface without compromising immediate bonding. BG reactivity and ion release (calcium, silicon, phosphate) likely explain the enhanced biomechanical behavior of the adhesive interface.