Electrostatic self-assembly of graphene oxide on TiO2 particles and their applications in dental restorative composites

Graphene oxide (GO), as a two-dimensional layered material, possesses excellent mechanical property and biocompatibility, which is of great importance in the field of dentistry. However, its dark-brown color negatively affects the esthetic appearance of dental restorative composites. In this study, the core-shell GO-wrapped TiO 2 (GO x @TiO 2 ) particles were synthesized via the electrostatic self-assembly, and their optical property was precisely tuned by varying the weight ratio of GO to TiO 2 ( x = 0.005, 0.01, 0.05 and 0.1) in the microemulsion system. All these hybrid particles were surface silanized and formulated with the dimethacrylate-based matrix at different fractions (0.5, 1 and 2 wt%) to develop dental composites under visible-light curing. As a result, the GO 0.005 @TiO 2 -filled composite achieved the highest light transmittance and the highest depth of cure among all materials, due to the light-grey and the lowest UV absorbance of GO 0.005 @TiO 2 . Furthermore, the optimal 1 wt% GO 0.005 @TiO 2 was selected to construct the bimodal filler formulation with micron-sized barium glass powder (BGP), thereby increasing the total filler fraction to 60 wt%. The 1G59B-filled composite exhibited the highest flexural strength (127.3 ± 13.5 MPa), compressive strength (315.4 ± 11.9 MPa) and fracture energy (2.6 ± 0.2 MJ/M 3 ) than those of the 1 wt% GO 0.005 @TiO 2 -filled composite (97.3 ± 11.9 MPa; 272.8 ± 20.8 MPa; 1.9 ± 0.2 MJ/M 3 ) and the resin matrix (67.8 ± 10.2 MPa; 216.6 ± 21.4 MPa; 2.3 ± 0.2 MJ/M 3 ), respectively, without affecting cell activity in vitro . This optimal composite also exhibited satisfactory water sorption and solubility. The introduction of GO 0.005 @TiO 2 particles and the bimodal filler provides a new approach for making high-strength dental composites and other related biomaterials. • The GO-wrapped TiO 2 (GO x @TiO 2 ) particles were made by electrostatic self-assembly. • The composition of GO x @TiO 2 hybrid particles affected their morphology and optical property. • Barium glass powder was used as the co-filler to formulate the bimodal filler formulation. • The 1G59B-filled composite produced the highest mechanical property without affecting cell viability.