The bioactivity of a series of fluoride-containing sodium-free calcium and strontium phosphosilicate glasses has been tested in vitro. Glasses with high fluoride content were partially crystallised to apatite and other fluoride-containing phases. The bioactivity study was carried out in Tris and SBF buffers, and apatite formation was monitored by XRD, FTIR and solid state NMR. Ion release in solutions has been measured using ICP-OES and fluoride-ion selective electrode. The results show that glasses with low amounts of fluoride that were initially amorphous degraded rapidly in Tris buffer and formed apatite as early as 3 h after immersion. The apatite was identified as fluorapatite by ¹⁹F MAS-NMR after 6 h of immersion. Glass degradation and apatite formation was significantly slower in SBF solution compared to Tris. On immersion of the partially crystallised glasses, the fraction of apatite increased at 3 h compared to the amount of apatite prior to the treatment. Thus, partial crystallisation of the glasses has not affected bioactivity significantly. Fast dissolution of the amorphous phase was also indicated. There was no difference in kinetics between Tris and SBF studies when the glass was partially crystallised to apatite before immersion. Two different mechanisms of apatite formation for amorphous or partially crystallised glasses are discussed.

Poor bonding stability remains the “Achilles' heel” of dentin bonding, a simple and effective approach to inhibit the activities of both exogenous collagenases and endogenous MMPs, and prevention of the growth of bacterial biofilm is therefore highly demanded. In the present study, a quercetin/ethanol solution was developed as a multifunctional primer to pretreat the dentin surface during adhesive restoration. The results showed that pretreatment with quercetin/ethanol solutions (0.5 and 1.0 wt%) on the dentin surface effectively preserved the bonding strength after one-month of collagenase aging (p < 0.05). Irrespective of aging, lower nanoleakage expression and less cohesive failure in dentin were observed in the quercetin-treated groups (p < 0.05). Compared with the control group, the in situ zymography test revealed that the 0.5 and 1.0 wt% quercetin-treated dentin effectively inhibited MMP activity, while their contact angles significantly increased. Live/dead bacterial staining and the MTT assay demonstrated that the 0.5 and 1.0 wt% quercetin groups exerted significant bactericidal effects while inhibiting biofilm growth of Streptococcus mutans (p < 0.05). We believe that a quercetin/ethanol solution might serve as a simple but versatile primer to provide dentists with a promising approach to obtain desirable bonding stability and to prevent secondary caries, thereby preventing the frequent replacement of resin-based restorations.