The purpose of this study was to investigate the effects of Bioglass 45S5 and Biosilicate, on bone defects inflicted on the tibia of rats. Fifty male Wistar rats were used in this study, and divided into five groups, including a control group, to test Biosilicate and Bioglass materials of two different particle sizes (180-212 microm or 300-355 microm). All animals were sacrificed 15 days after surgery. No significant differences (P > 0.05) were found when values for Maximal load, Energy Absorption and Structural Stiffness were compared among the groups. Histopathological evaluation revealed osteogenic activity in the bone defect for the control group. Nevertheless, it seems that the amount of fully formed bone was higher in specimens treated with Biosilicate (granulometry 300-355 microm) when compared to the control group. The same picture occurred regarding Biosilicate with granulometry 180-212 microm. Morphometric findings for bone area results (%) showed no statistically significant differences (P > 0.05) among the groups. Taken together, such findings suggest that, Biosilicate exerts more osteogenic activity when compared to Bioglass under subjective histopathological analysis.