The purpose of this study was to determine the effect of root dentin hardness after placement of different intra canal medicaments such as Nano silica TAP, TAP and calcium hydroxide. forty-five freshly extracted third molars were sectioned, with thickness of 1.5 mm dentin disc, after which each sample was irrigated with 20 ml of 1.5 percent sodium hypochlorite (Naocl). Teeth were randomly divided into three groups (n = 15): group-1 TAP, group-2 Nano-silica TAP, and group-3 calcium hydroxide. The radicular side of each dentin disc was treated with the medicament by applying 0.1 ml of TAP, Nano TAP, and calcium hydroxide. Each specimen were subjected to micro-hardness testing using a Vickers micro-hardness tester. Statistical analysis was done using one way Analysis of Variance (ANOVA), Post-Hoc Tukey test and Paired t-test to compare the pre and post immersion micro-hardness values of the selected samples.The result of the present study shows significantly increase the micro-hardness of root dentin in Nano TAP compared to TAP and calcium hydroxide group. Thus Nano-silica can be added to TAP and used as an intracanal medicament and improves its antimicrobial property.