Synthesis of core-shell structured ZnO@m-SiO2 with excellent reinforcing effect and antimicrobial activity for dental resin composites

Objective. The aim of this study is to explore the reinforcing effect and the antimicrobial activity of the core-mesoporous shell structured ZnO@m-SiO2, which possesses the micromechanical resin matrix/filler interlocking in dental composites, and to investigate the effect of filler compositions on their physical-mechanical properties. Methods. ZnO@m-SiO2 was synthesized by a simple self-assembly method and then characterized by electron microscopy, X-ray diffraction (XRD) and N-2 adsorption/desorption measurements. Mechanical properties of dental composites reinforced with ZnO@m-SiO2 and nonporous SiO2 particles were measured with a universal mechanical testing machine. Fracture morphologies of these composites were observed by field-emission scanning electron microscopy (FE-SEM), and their antimicrobial activities were evaluated according to the ASTM E 2180-07 (2012) method. Resin composites containing unimodal silanized SiO2 were served as the control group. Results. The impregnation of lower loading of ZnO@m-SiO2 (<= 7 wt%) into dental composites including silanized SiO2 substantially increased their mechanical properties. Among all composites, the optimal composite Z(7)S(63) (ZnO@m-SiO2 : silanized SiO2 = 7:63, wt/wt, total filler loading 70 wt%) demonstrated the best flexural strength, flexural modulus and compression strength, which were increased by 121.2, 67.1 and 32.5%, respectively, in comparison with the control composite Z(0)S(70). In addition, this optimal composite also exhibited superior antimicrobial activity (>99.9%) and acceptable degree of conversion, polymerization shrinkage and curing depth. Significance. The incorporation of ZnO@m-SiO2 and silanized SiO2 as bimodal fillers led to the design and formulation of dental composites with excellent comprehensive performance, especially the improved mechanical properties and the superior antimicrobial activity. (C) 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.