Short- and Long-Term Dentin Bond Strength of Bioactive Glass-Modified Dental Adhesives

This study investigated the short- and long-term effects of dental adhesives doped with nano-sized bioactive glass 45S5 (BAG) on the resin-dentin interfacial bond strength. Two etch-and-rinse adhesives (Adper Scotchbond Multi-Purpose (ASB) and Solobond Plus (SB)) and one self-etch adhesive (Clearfil SE Bond (CF)) were doped with different concentrations of BAG (5, 10, and 20 wt%). The unmodified (0 wt% BAG) commercial adhesives served as control groups. Dentin of 120 molars (n = 10 per group) was treated with the different adhesives, followed by buildups with a conventional composite restorative material. From each tooth, 14 sticks were prepared for micro-tensile bond strength (µTBS) testing. The sticks were stored in simulated body fluid at 37 °C and tested after 24 h or six months for µTBS and failure mode. Data were analyzed using Kruskal-Wallis tests in combination with post-hoc Conover-tests and Wilcoxon signed-rank tests at a level of significance of α = 0.05. After 24 h and six months, both etch-and-rinse adhesives with a low BAG content (up to 10 wt% for ASB and 5 wt% for SB) showed similar µTBSs as their respective control groups (0 wt% BAG). CF showed a significant decrease in µTBS even after addition of 5 wt% BAG. At a high concentration of added BAG (20 wt%), all three adhesives showed a significant decrease in µTBS compared to the unmodified controls. The CF control group showed significantly lower µTBS after 6 months of storage than after 24 h. In contrast, the µTBS of all CF groups modified with BAG was unaffected by aging. In conclusion, the tested etch-and-rinse adhesives can be modified with up to 5 wt% (SB), or 10 wt% (ASB) of BAG without reducing their short- and long-term dentin bond strength. Moreover, the addition of nano-sized BAG may prevent long-term bond strength deterioration of a self-etch adhesive.