Synthesis and characterization of graphene oxide-zirconia (GO-ZrO2) and hydroxyapatite-zirconia (HA-ZrO2) nano-fillers for resin-based composites for load-bearing applications

Abstract

ObjectivesThe study aims to synthesize two different types of nano-fillers based on zirconia (ZrO2), which was functionalized with graphene oxide (GO-ZrO2), and hydroxyapatite (HA-ZrO2), and to implement them in an experimental methacrylate matrix containing new dimethacrylic oligomers. MethodsNano-particles were synthesized via a modified Hummer’s method and a sol-gel route. Bisphenol A-glycidyl methacrylate oligomers (Bis-GMA336[0–1]) were synthesized from an epoxy resin that reacted with methacrylic acid in the presence of a basic catalyst. Traditional dental glass-fillers (Barium oxide/BaO and Barium fluoride/BaF2) were synthesized to create an experimental resin-based composite (RBC) used as reference. Filler morphology was evaluated via Transmission Electron Microscopy. RBCs were characterised by real-time Fourier transform infrared spectroscopy (degree of cure/DC, polymerisation kinetics), real-time spectrometry (light transmittance), 3-point bending test (flexural strength and modulus, Weibull parameters), and depth-sensing indentation test (plastic and elastic deformation parameters). ResultsThe synthesized nanohybrid fillers proved good dispersing performance. Mechanical properties and materials’ reliability are within or above the mean values reported in the literature for RBCs. Addition of HA-ZrO2-fillers resulted in a decrease light transmission, DC and mechanical properties. Except for the HA-ZrO2 RBC, materials showed a high resistance to softening in solvent. ConclusionsThe synthesis of GO-ZrO2 and HA-ZrO2 nanohybrid particles and their implementation in experimental RBCs has proven successful. Adjustments of the light transmission through suitable co-fillers in addition to GO-ZrO2 as well as adjustments of the amount of HA-ZrO2 are necessary to enable reduced curing time (<20 s). Clinical significanceThe addition of nanofillers with tailor-made properties can help improving the performance of modern restoratives.