Isfahan University of Medical SciencesDental Research Journal1735-33279320120821The effect of nanoclay filler loading on the flexural strength of fiberreinforced composites10841084ENVajihesadatMortazaviTorabinejad Dental Research Center and Department of Operative Dentistry, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran. v_mortazavi@dnt.mui.ac.irMohammadAtaiMohammadhosseinFathiSolmazKeshavarziNavidKhalighinejadHamidBadrian20120821Background: Flexural strength of prosthesis made with dental composite resin materials plays animportant role in their survival. The aim of this study was investigating the effect of nanoclay fillersand Poly (methyl methacrylate)-grafted (PMMA-grafted) nanoclay fillers loading on the flexuralstrength of fiber-reinforced composites (FRCs).Materials and Methods: Standard FRC bars (2 × 2 × 25 mm) for flexural strength testing wereprepared with E-glass fibers and a synthetic resin loaded with different quantities of unmodifiednanoclay and PMMA-grafted nanoclay filler particles (0% as control group, 0.2%, 0.5%, 1%, 2%, 5%).Flexural strength and flexural modulus were determined. The data were analyzed using 2-way, 1-wayANOVA and post hoc Tukey’s test (a = 0.05). The fracture surfaces were evaluated by ScanningElectron Microscopy.Results: For groups with the same concentration of nanoparticles, PMMA-grafted filler-loaded groupshowed significantly higher flexural strength, except for 0.2% wt. For groups that contain PMMA-graftednanoclay fillers, the 2% wt had the highest flexural strength value with significant difference to othersubgroups. 1% wt and 2% wt showed significantly higher values compared to control (P < 0.05). Noneof the unmodified nanoclay particles loaded group represented statistically higher values of flexuralstrength compared to control group (P > 0.05). Flexural modulus of 2%, 5% wt PMMA-grafted and0.5%, 1%, 2%, 5% wt unmodified nanoclay particles-loaded subgroups decreased significantlycompared to control group (P < 0.05).Conclusions: PMMA-grafted nanoclay filler loading may enhance the flexural strength of FRCs.Addition of unmodified nanoparticles cannot significantly improve the flexural strength of FRCs.Addition of both unmodified and PMMA-grafted nanoclay particles in some concentrations decreasedthe flexural modulus.Key Words: Fiber-reinforced composite, flexural modulus, flexural strength, nanoclay particle