Composite resin reinforced with silver nanoparticles-laden hydroxyapatite nanowires for dental application

Objective The object is to find a functional one-dimensional nanofibrous filler for composite resin, which is able to provide both efficient reinforcement and high antibacterial activity. Methods. Hydroxyapatite (HA) nanowires were synthesized via hydrothermal technique using calcium oleate as the precursor. Polydopamine (PDA)coated HA (HAPDA) nanowires were prepared by soaking HA nanowires in dopamine (DA) aqueous solution. Silver nanoparticles (AgNPs)laden HA (HAPDAAg) nanowires were prepared via reduction reaction by adding silver nitrate and glucose into HAPDA suspensions in DI water. The resulted HAPDAAg nanowires were then mixed into Bis-GMA/TEGDMA (50/50, w/w) at 410 wt.%, thermal-cured, and submitted to characterizations including mechanical properties, interfacial adhesion between filler and resin matrix, distribution of HA nanowires and AgNPs, as well as silver ion release, cytotoxicity and antibacterial activity. Results. HAPDAAg nanowires were readily obtained and the loading amounts of AgNPs could be controlled by adjusting the feeding doses of silver nitrate and HAPDA nanowires. Benefiting from the PDA surface layer, HAPDAAg nanowires could disperse well in composite resin and form good interfacial adhesion with the resin matrix. In comparison with neat resin, significant increases in flexural strength and modulus of cured composites were achieved at the addition amounts of HAPDAAg nanowires being 68 wt.%. The distribution of AgNPs was homogeneous throughout the resin matrix in all designs, which endowed the composites with high antibacterial activity against streptococcus mutans. Continuous silver ion release from composites was detected, however, it was determined the composites would have insignificant cytotoxicity based on the proliferation of L929 fibroblasts in extracts of HAPDAAg nanowires. Significance. The finding proved that HAPDAAg nanowires could serve as functional nanofillers for composite resins, which should help much in developing materials for satisfactory long-term clinical restorations. (C) 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.