The properties of dental resin composites reinforced with silica colloidal nanoparticle clusters: Effects of heat treatment and filler composition

Resin composites have been frequently applied in dental restoration due to their distinguished overall performance. The size, structure and composition of inorganic fillers have significant effects on the properties of dental resin composites (DRCs). The aim of our research is to strengthen the structure of spray-dried silica colloidal nanoparticle clusters (SCNCs) by means of a calcination process, and achieve the excellent comprehensive performance of DRCs by the combined use with different fillers. The results indicate that the SCNCs calcined at 500 °C has a significant strengthening effect on the flexural properties and hardness of DRCs except the decrease of compressive strength in comparison to the uncalcined SCNCs. To overcome this problem, the SiO2 nanoparticles (NPs) as building blocks for SCNCs and the SCNCs were further adopted as co-fillers of the calcined SCNCs (CSCNCs). It can be found that the strengthening effect of SCNCs is better than that of the NPs at the same filling ratio. The DRCs filled with 60 wt% CSCNCs and 10 wt% SCNCs have a greatly enhanced compressive strength, reaching the same level with the DRCs filled with 70 wt% SCNCs. More importantly, the corresponding flexural strength (143.5 ± 8.3 MPa), flexural modulus (8.91 ± 0.48 GPa) and hardness (70.7 ± 1.4 HV) still have an improvement of 14%, 23% and 48% in comparison with those of the counterpart, respectively.