An In Vitro Evaluation of the Antibacterial and Remineralizing Efficacy of a Silver Nanoparticle-Containing Toothpaste

Introduction This in vitro study aimed to compare the antibacterial action and microhardness effect on enamel of a toothpaste containing silver nanoparticles (SNPs) with three other preparations. Methods Four types of toothpaste were tested: one containing SNPs, one without SNPs, a probiotic toothpaste, and Signal toothpaste. Antibacterial activity against Streptococcus mutans was assessed using disc diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) assays. To evaluate remineralization, 40 extracted human third molars underwent pH cycling for one week, followed by Vickers hardness testing. Antibacterial results were analyzed with the Kruskal-Wallis test, and remineralization data with repeated measures ANOVA and Games-Howell post-hoc tests (α = 0.05). Results Signal toothpaste showed significantly smaller inhibition zones compared to the other three groups ( p < 0.05). The SNP-toothpaste exhibited the lowest MBC, indicating the strongest bactericidal effect, while the control toothpaste with no SNPs showed the weakest activity (highest MIC and MBC). No significant differences in enamel microhardness were observed among the four groups after treatment ( p > 0.05). Discussion The SNP-containing toothpaste demonstrated greater bactericidal efficacy against S. mutans, but its effect on enamel surface hardness was similar to the other fluoridated toothpastes. Conclusion SNP toothpaste showed superior antibacterial activity but did not improve enamel hardness beyond other fluoride-containing toothpastes.