Cytotoxicity, antibacterial efficacy, and fluoride content of commercial herbal toothpastes

Abstract

This study evaluated fluoride concentration, antibacterial activity against Streptococcus mutans, and cytotoxicity of commercially available herbal toothpastes to assess their safety and clinical potential. Fifteen herbal toothpastes were tested. Fluoride concentration was measured using a fluoride ion-selective electrode. Antibacterial activity against S. mutans was assessed by agar diffusion, and cytotoxicity was evaluated using the MTT assay in L929 fibroblasts and human gingival fibroblasts. Antibacterial and cytotoxicity data were analyzed using one-way ANOVA with Tukey’s HSD test, fluoride concentrations using the Kruskal–Wallis test, and associations among the three outcomes using Spearman’s rank correlation. Fluoride concentrations varied considerably, with 66.67% of products containing less than 600 ppm and only 20% reaching approximately 1500 ppm. Most products did not clearly indicate fluoride type or concentration on their labels. Strong antibacterial activity, with inhibition zones of 2.12–2.18 cm comparable to vancomycin, was observed in 26.67% of samples (p < 0.05). LC₅₀ values ranged from 0.715 to 9.410, and four formulations showed high cytotoxicity (p < 0.05). Antibacterial activity was inversely correlated with the LC₅₀ of L929 cells (rs = −0.579, p < 0.001) and of human gingival fibroblasts (rs = −0.328, p < 0.05), whereas fluoride concentration showed no association with greater cytotoxicity. Herbal toothpastes with strong antibacterial effects often showed moderate to high cytotoxicity. Formulations containing biocompatible ingredients, antioxidants, and adequate fluoride may provide a safer balance, highlighting the need for clearer labeling and optimized ingredient concentrations.