Dental caries is one of the most prevalent epidemic and chronic mammalian diseases all over the world. Streptococcus mutans is the leading cause of dental caries (tooth decay) worldwide. Over the last few decades there has been a remarkable increase in its prevalence rate among children and elders. Multidrug resistant S.mutans arose recent past decade. All the samples were collected from the dental clinics in Tirupur district of Tamilnadu. All the isolates were identified and characterized by biochemical reaction. Antibiotic susceptibility test was performed by disc diffusion assay. Tested isolates were showed resistant against six antibiotics. Nalidixic acid exhibited 100% resistant against all the ten isolates. Antibacterial activity was carried out by well diffusion method. Different concentrations of NaF (0.01%, 0.02%, 0.03%, 0.04% and 0.05%) were showed absence of inhibition against tested isolates.