Cytotoxicity and antibacterial effects of sodium phytate- and bromelain-containing experimental toothpastes for pediatric black stain management: an in vitro study

Background: Black stain is a common form of extrinsic tooth discoloration in pediatric patients. Recently, interest in home-care strategies, such as toothbrushing with specialized toothpaste formulations, has increased. Natural ingredients, including sodium phytate and bromelain, have been proposed as alternatives to conventional whitening agents for managing black stain; however, their cytotoxic and antibacterial performance remains unclear. Therefore, this study aimed to evaluate the cytotoxicity and antibacterial activity of two experimental toothpaste formulations for black stain management. Methods: Three toothpaste groups were tested: Group A (0.85% w/w sodium phytate, fluoride-free), Group B (5% w/w bromelain, fluoride-free), and Group C (commercial children’s toothpaste, 500 ppm fluoride), all containing sodium lauryl sulfate (SLS) as a common surfactant. Cytotoxicity was assessed using the XTT (sodium 3′-(1-phenylaminocarbonyl)-3,4-tetrazolium-bis(4-methoxy-6-nitro)benzenesulphonic acid) assay on L929 cells at six serial dilutions (1:1–1:32) with exposure times of 1, 2, and 5 minutes. Cell viability below 70% was considered cytotoxic according to the International Organization for Standardization (ISO) 10993-5. Antibacterial efficacy against Streptococcus mutans (S. Mutans) was assessed using agar-well diffusion. Penicillin-streptomycin and distilled water served as positive and negative controls, respectively. Results: All toothpaste formulations reduced cell viability below 70% at dilutions from 1:1 to 1:8. At the 2-minute exposure and 1:8 dilution, Group A was the most cytotoxic, followed by Group B, whereas Group C exhibited the highest cell viability (p < 0.001). All formulations demonstrated significant antibacterial activity against Streptococcus mutans. Group A’s inhibition zone (19.54 ± 0.99 mm) was comparable to the positive control (p > 0.05) and significantly greater than Groups B and C (p < 0.05), which were comparable to each other (p > 0.05). Conclusions: While the experimental toothpastes demonstrated antibacterial activity, their cytotoxic potential warrants caution, and studies optimizing formulation composition, including SLS-free or fluoride-containing alternatives, are needed to confirm clinical safety and applicability.

Bromelain; Sodium phytate; Dentifrices; Sodium lauryl sulfate; Antibacterial efficacy; Iron stain

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