Many herbal toothpastes fell short on a key cavity-fighting ingredient

Tests of 15 commercial herbal toothpastes revealed wide differences in fluoride, antibacterial activity, and cytotoxicity, with some formulations showing that strong bacterial inhibition does not have to come at the expense of cellular safety.

Herbal toothpastes with strong antibacterial activity often exhibit moderate to high cytotoxicity, according to a new laboratory study published in BDJ Open.

Herbal toothpastes raise fluoride and safety questions

Dental caries is a multifactorial disease mediated by oral biofilms and driven by dietary sugars. Acidogenic and aciduric bacteria such as Streptococcus mutans present in the oral cavity metabolize dietary fermentable carbohydrates to produce organic acids, which in turn induce demineralization of the tooth enamel and promote progressive loss of minerals from dental tissues.

Maintaining oral hygiene through regular brushing with fluoride-containing toothpaste effectively prevents dental caries because fluoride promotes remineralization and reduces demineralization during repeated acid challenges.

Herbal oral healthcare products, including herbal toothpastes and mouthwashes, are gaining popularity in recent times in part because consumers may perceive them as safer or as having fewer side effects than conventional dental care products containing synthetic chemicals.

In Thailand, toothpaste is considered a cosmetic product, for which fluoride content should not exceed 1500 ppm (parts per million). At the time the products were purchased and analyzed, Thai regulations did not require manufacturers to declare fluoride concentrations on toothpaste labels; a labeling requirement has since taken effect.

Given the increasing popularity of herbal toothpaste in Thailand, researchers examined fluoride content, antibacterial efficacy against Streptococcus mutans, and cytotoxicity of 15 commercially available toothpastes marketed as herbal, natural, or containing herbal-derived ingredients to evaluate their safety profiles and clinical potential.

Low fluoride levels common across tested toothpastes

Fluoride analysis showed that 10 of the 15 toothpastes (66.7%) contained less than 600 ppm, and only three (20%) contained approximately 1500 ppm.

Among tested herbal toothpastes, only four exhibited strong antibacterial activity against Streptococcus mutans. Their antibacterial efficacy in the laboratory assay, measured by inhibition-zone size, was comparable to that of vancomycin, which served as a positive control.

Regarding cytotoxicity, several formulations markedly reduced fibroblast viability, although the products showing the greatest cytotoxicity differed between mouse fibroblasts and human gingival fibroblasts.

The analysis comparing three study outcomes indicated that antibacterial activity was associated with greater cytotoxicity. However, fluoride content showed no association with antibacterial activity and was not associated with greater cytotoxicity; if anything, higher fluoride concentrations showed a weak association with lower cytotoxicity.

Herbal formulas can balance fluoride, efficacy and safety

The study reports that most tested commercially available herbal toothpastes have low fluoride content. Antibacterial activity and cytotoxicity, however, varied significantly across formulations, with toothpastes with strong antibacterial activity often showing moderate to high cytotoxicity.

Herbal toothpastes are prepared using plant-based ingredients, including neem, clove, cinnamon, coconut, lemon, spearmint oils, and guava leaf extract. Several bioactive compounds in these ingredients are well known for their oral health-promoting properties, such as anti-inflammatory and antimicrobial effects.

According to the Dental Association of Thailand, toothpastes for individuals aged 6 years and older should contain 1400-1500 ppm of fluoride, whereas 1000 ppm of fluoride is generally recommended for younger children.

However, only three out of 15 toothpastes analyzed in the study had fluoride content of approximately 1500 ppm. The reasons for omitting fluoride were unclear, although the researchers speculated that manufacturers may avoid using it because it can affect the consistency and taste of toothpaste. Another possible reason is to meet consumer demand for natural, plant-based formulations free of synthetic chemicals.

These findings concern consumers because herbal toothpastes with inadequate fluoride may provide less effective protection against dental caries. Three toothpastes that had adequate fluoride concentrations together with effective antibacterial activity and low cytotoxicity highlight the fact that a herbal formulation and an effective fluoride concentration are not mutually exclusive.

These findings should encourage manufacturers to include recommended amounts of fluoride in herbal toothpastes to provide consumers with evidence-based protection against dental caries.

Four out of 15 tested toothpastes showed strong antibacterial activity against harmful oral bacteria such as Streptococcus mutans. The researchers suggest that the strong antibacterial activity may be attributable to certain bioactive ingredients present in these toothpastes, such as guava extract, licorice extract, peppermint extract, clove oil, and cinnamon oil. Certain chemical ingredients may also potentially contribute to this activity, including sodium monofluorophosphate, sodium bicarbonate, and sodium chloride. Future research is needed to explore the specific contribution of individual ingredients to the antibacterial activity. s41405-026-00489-y s41405-026-00489-y

An ideal herbal toothpaste should have antibacterial activity without inducing cytotoxicity, while maintaining an effective fluoride concentration for caries prevention. However, the study identified several formulations with relatively high cytotoxicity, possibly due to the cell membrane-disrupting and oxidative stress-inducing effects of certain bioactive ingredients, including clove oil, camphor, menthol, borneol, and peppermint.

In contrast, one toothpaste containing antioxidant-rich plant extracts and a mild surfactant showed the lowest cytotoxicity, highlighting the need for optimized ingredient concentrations in herbal toothpaste.

Taken together, the study findings suggest that the antibacterial effects of herbal toothpastes may be driven by bioactive ingredients other than fluoride. Further clinical studies are necessary to assess the long-term safety and effectiveness of these products.

All experiments in this study were conducted in artificial laboratory environments, which may not fully reflect real-life oral health conditions. The findings therefore do not account for individual variations, daily oral care habits, and long-term effects. Further clinical validation and studies using additional cariogenic species, multispecies biofilm models, and more replicates are required for more conclusive inferences.

Journal reference:

• Poeaim N. (2026). Cytotoxicity, antibacterial efficacy, and fluoride content of commercial herbal toothpastes. BDJ Open. DOI: https://doi.org/10.1038/s41405-026-00489-y. https://www.nature.com/articles/s41405-026-00489-yhttps://www.nature.com/articles/s41405-026-00489-y