Antibacterial and metalloproteinase-inhibited zinc-doped bioactive glass nanoparticles for enhancing dentin adhesion

Objectives: Novel zinc-doped bioactive glass nanoparticles (ZnBGNs) were designed for dental adhesive to enable multifunctional properties for dentin bonding durability. Methods: ZnBGNs were synthesized via the sol-gel template method and characterized via TEM, SEM and EDS. ZnBGNs were added from 2.5wt% to 10wt% to Adper™ Single Bond 2 adhesive (SB2). The effects of ZnBGNs on the degree of conversion, contact angle and antibacterial activity were measured. Endogenous matrix metalloproteinases (MMPs) activity, Young's modulus of the hybrid layer, microtensile bond strength and interfacial nanoleakage were investigated after 24 h and 3 months ageing in artificial saliva. Results: ZnBGNs exhibited good monodispersity, bioactivity activity and superior antimicrobial activity. Adding no >5 wt% ZnBGNs had no adverse effects on the degree of conversion and contact angle of the SB2 Control (p > 0.05). Incorporating ZnBGNs dramatically reduced the endogenous MMPs activity, facilitated remineralization and increased the Young's modulus of the hybrid layer after 3 months ageing (p < 0.05). Dentin bond strength had 44 % loss with increased nanoleakage after 3 months of ageing for SB2 Control. However, SB2+2.5 wt% ZnBGNs showed no loss in bond strength and the least degree of nanoleakage after 3 months ageing (p < 0.05). Conclusions: Incorporating ZnBGNs into dental adhesive systems can provide antimicrobial, anti-metalloproteinase and remineralization microenvironments, which indicates a suitable strategy to prevent the degradation of hybrid layers. Clinical Significance: ZnBGNs with multifunctional properties will likely be used to prevent the degradation of hybrid layers, thereby extending the longevity of resin-dentin bonds.