Bioactivity and adhesion of an experimental bioactive glass-containing bonding system

Objectives: bioactive/resin-based materials may promote healing of mineral-deficient resin-dentine interfaces. The aim of this study was to evaluate the 6-month bond strength durability of an experimental “etch & rinse”, bioglass-containing adhesive. The bioactivity in the remineralization of mineral-deficient resin-dentine interfaces was evaluated using confocal micro-Raman spectroscopy. Methods: Twenty dentine crowns were etched with 37%-H3PO4 for 15s. The specimens were primed (Bis-GMA, TEGDMA, HEMA and 50%-ethanol) and bonded using two different adhesive systems: Control (Bis-GMA, TEGDMA, HEMA) or Bioactive: (Bis-GMA, TEGDMA, HEMA, bioactive glass); light curing was performed for 20s. 5mm incremental build-ups were made using Filtek Z250 (3M-ESPE) and photo-cured for 30 seconds. Half of the specimens were tested for microtensile bond strengths (MTBS) after 24h and half after 6-months of PBS storage. The MTBS results were compared statistically and the differences were identified among the groups by two-way ANOVA; adhesive system, and water storage were considered as independent variables (P < 0.01). Fisher's least significant difference (LSD) test was used to isolate and compare the significant differences (P < 0.05) between the groups. Additional dentine surfaces were bonded as previously described. These were prepared, sectioned, polished and analysed using confocal micro-Raman spectroscopy after 24h and after 6 months of PBS storage. Results: mean (SD) MTBS values for each group are shown in the table. The confocal micro-Raman spectroscopy showed signs of hydroxyapatite formation within and underneath the hybrid layer. Conclusions: although both the experimental bonding agent used in this study showed a statistical reduction of the bond strength after 6-month aging, the use of the bioactive experimental bonding agent may have a “therapeutic” characteristic to remineralize mineral-deficient resin-dentine interfaces.