The influence of nanofiller particle size and surface treatment on dental composite

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] In the present study, the effect of the size-scale combination of silica on the mechanical and optical properties of acrylate-based (50% BisEMA and 50% UDMA by weight) composites is examined, with the aim of investigating and optimizing the properties of nano-sized particle-filled composites typically used in restorative dentistry. Three classes of light-cured composites were prepared with various size-scale combinations of silica (7 nm + 0.7 [micro]m; 12 nm + 0.7 [micro]m; 40 nm + 0.7 [micro]m) as the filler. The weight fraction of fillers was 60 wt%, and the weight fraction of fumed silica ranged from 1 wt% to 9 wt%, with an increment of 2 wt% and two more group with 0 wt% as contro and 4 wt% as additional contrast. The flexural strength and Vickers hardness were characterized as mechanical properties. The microstructure of the fractured surfaces of samples were characterized by scanning electron microscope (SEM). The characterizations showed a well and even dispersion. For each nano-sized fumed silicaincorporated composite, there is a relatively optimal weight percentage range and surface treatment parameter to yield ideal flexural strength. In general, adding fumed silica increased the hardness. 7 nm reinforced composites with 4 wt% had the highest surface hardness with about a 35% increase. The optical properties were investigated on a VITA Easyshade compact spectrophotometer. Based on the CIELAB system, larger particles incorporated into a composite tended to make the sample brighter, yellower and greener. In terms of translucency parameter, particle size did not dramatically influence the translucency parameter. Higher weight percentage of fumed silica yielded a lower translucency parameter and opaque material. In general, adding fumed silica increased viscosity. Small particles and higher weight percentage yielded higher viscosity