The aim of this study is to evaluate the antibacterial action Nano Silver Fluoride solution application in comparison to Chlorhexidine solution after partial caries removal in class I carious permanent molar. Based on a previous study by Mohan et al. 20165, the expected difference between two interventions is expected to be 2.1±2.2CFU/mL × 103. Using power 80% and 5% significance level we will need to study 18 in each group to be able to reject the null hypothesis that the population means of the experimental and control groups are equal. This number is to be increased to 22 patients in each group to compensate for possible losses during follow up. The sample size was calculated by PS program.