Antibacterial Composite Resin Reinforced With Nano-Silver Loaded Hydroxyapaptite Nanowires For Dental Restoration

With the wide use of computer-aided design and computer-aided manufacturing (CAD/CAM) in dental restoration, various kinds of machineable materials that are matched with the CAD/CAM system have gradually become the focus of researchers. Compared to ceramic and metallic materials, machinable composite resins demonstrate obvious advantages in the manufacture of personalized temporary or long-term restorations.In this thesis, nano-silver loaded hydroxyapatite (HA) nanowires with one-dimensional structure were synthesized via hydrothermal method, followed by surface treatments of dopamine and silver nitrate aqueous solutions in sequence. The resulted HA nanowires, having Ag nanoparticles (AgNP) homogeneously distribution on surface, displayed good interfacial binding with acrylate resins benefiting from the universal binding ability of the dopamine structure. Therefore, these AgNP-loaded HA nanowires could be used as dual functional nanofillers in Bis-GMA/TEGDMA composite resin to provide both reinforcement and with antibacterial activity. The main contributions of the present work are listed as follows:1. HA nanowires were prepared via hydrothermal method by using calcium dioleate and sodium dihydrogen phosphate as the precursors. Reaction parameters were optimized by investigating the effects of reaction temperature and time on the morphology and crytallinity of HA products. As the result, one-dimensional HA nanowires with fine morphology were obtained by setting the reaction temperature at 180? and the reaction time as 23 h. Then, dopamine aqueous solution was applied to coat these HA nanowires with a layer of polydopamine.2. Subsequently, the polydopamine-coated HA nanowires were dispersed in aqueous solution containing polyvinylpyrrolidone, sucrose and silver nitrate. AgNPs formed via the Tulane reaction and deposited onto HA nanowires owing to the binding ability of polydopamine. The content of AgNPs being loaded onto HA nanowires could be controlled by adjusting the ratio of AgNO3 to HA nanowires. All the AgNP-loaded HA nanowires demonstrated high antibacterial activity against streptococcus mutans (S.M.), however, non-cytotoxicity against L929 fibroblasts was achieved only when the concentration of silver ion in the extract was below 1.6ppm.3. Thereafter, composite resins were made by mixing different ratios of AgNP-loaded HA nanowires into the Bis-GMA/TEGDMA (w:w= 1:1), followed by thermocuring at 120? for 12 h using benzoyl peroxide (BPO) as radical initiator. Evaluations including three-point bending test and morphology observation on fractured surface were carried out. It was found that composite resins containing 6-8 wt.% of AgNP-loaded nanowires displayed high flexural strength, good antibacterial performance and low cytotoxicity. The nanowires could be seen binding firmly to the resin matirx and dispersing homogeneously when the content was not higher than 8 wt.%.In summary, the AgNP-loaded HA nanowires have the potentials to be used as functional nanofillers for high-performance composite resins, which are targeting for CAD/CAM-based applications in dental restoration.