The biolfilms are the main cause of failure of root canal treatment (RCT) due to secondary infection. The main aim of the endodontic therapy is elimination of complex biofilms. During RCT while irrigating various solutions like EDTA, sodium hypochlorite (NaOCl), chlorhexidine (CHX) are applied at various concentrations for the eradication of the smear layer. Special attention has been given on effectiveness of irrigation to remove of smear layer in numerous studies conducted so far. The areas like isthmuses, fins and lateral canals which are relatively untouched by the files are effectively dealt with by irrigation. Antimicrobial nanoparticles have been developed to eliminate the limitations of routinely used antibacterial agents. Aim : To evaluate and compare the cytotoxicity Of 3% NaOCl, oxytetracycline, 2% CHX and triclosan combined with and without silver nanoparticle as endodontic irrigant on periodontal ligament cells using the Mosmann’s Tetrazolium Toxicity(MTT) assay . Materials and Methods: The roots of premolars extraxted for orthodontic purpose were used to grow periodontal cells (PDL). A water based incubator was used for culture at 37⁰C in a humidified atmosphere for 24 hours with 95% air and 5% CO2. After being divided randomly into nine experimental groups, cells were transplanted to 36-well plates. The Mosmann's Tetrazolium Toxicity assay was used for assessing cytotoxicity of the materials. The proportion of living cells affected how intense the colour was created. Descriptive statistics and repeated measures ANOVA followed by Tukey’s Post hoc Test for pairwise comparison were used for statistical analysis. Results: There was a statistically significant difference in the average number of viable cells between the tested irrigation solution and the control at different time interval (P 0.0001). Addition of silver nanoparticle reduces the cell viability in all the groups. All irrigants with addition of silver nanoparticles at all time intervals did not show any statistically significant difference.