the effect of aging and silanization on the mechanical properties of fumed silica-based dental composite

abstract statement of problem: mechanical strength and durability of dental composites are the main topics studied in this field of science today. this study examined fumed silica-based composite as a strong and durable restorative material through flexural and cycling test methods.     objectives: the purpose of this study was to evaluate the effect of silanization, ageing, cycling and hybridizing on mechanical properties of fumed silica-based resin composite. materials and methods:  composites were made of light-cured copolymer based on bisphenol a glycolmethacrylate (bis-gma) and triethylene glycoldimethacrylate (tegdma) at proportion of 50:50 which reinforced by fumed silica filler. for each composite sample, 5 specimen bars were made using teflon mould (2 x 2 x 25 mm 3 ). the samples with 12 wt% fumed silica (fs) were considered as a base line group. the samples were exposed to cyclic cold water (fs-ccw) and hot water (fs-chw). the effect of silanization and adding more filler was studied together with samples containing 12 wt% (fs-s (12), 16 wt% (fs-s (16) and 20 wt% (fs-s (20) fumed silica filler. the filler was silanized with (γ-mps). the degree of conversion was assessed with fourier transform infra-red spectroscopy. flexural properties were evaluated with the three-point bending test. flexural data were analyzed with excel software. hardness was measured with an atomic force microscope (afm). results: the degree of conversion of the resin reached 74% within 24 hrs. salinization allowed more filler to be wetted by resin. addition of silanized particles from sample fs-s (12) to sample fs-s (20) improved the mechanical strength. hybridizing fumed silica with nano-silica (fs-n) had no significant effect on the strength, but nano-hardness improved greatly. ageing and cycling had adverse effects on the strength of the sample fs. the flexural strength of fs-chw was 72% less than fs sample. conclusions: sample fs-n with low diluent and filler percentage complied with the requirements of flexural strength was established by iso 4049/2009 and may be cost benefit to be used as a dental composite for clinical application.