Tooth decay is one of the most common diseases in the oral cavity and is one of the most widespread diseases in the human population. This study aimed to determine the antibacterial effect of nickel oxide nanoparticles against bacteria involved in tooth decay. In this study, the disk diffusion method was used to determine the antibiotic susceptibility and the microdilution broth method was used to determine the minimum inhibitory concentration (MIC). Nanoparticles were also synthesized in two molecular size (A: 8.1 and B: 12 nm) by the sol-gel method. The MIC of the first nanoparticle for Streptococcus sanguinis and Streptococcus mutans was 31.25 and 125 μg/ml, respectively. The MIC of the second nanoparticle for S. sanguinis was 125 μg/ml. In the case of S. mutans up to a concentration of 500 μg/ml, no growth inhibition was observed. The results showed that nickel oxide nanoparticles have acceptable antibacterial properties against S. mutans and S. sanguinis, which can be used in dental materials to prevent dental caries. However, this requires the determination of cellular toxicity and its side effects in future studies.
