Efficacy of BioMin F and NovaMin toothpastes against *streptococcus mutans*: an *in vitro* study

Dental caries prevalence is high among children in Syria, driven by plaque accumulation, carbohydrate fermentation, acid production, and subsequent enamel and dentin demineralization. Streptococcus mutans is a key cariogenic pathogen due to its acidogenicity and extracellular matrix formation. While daily oral hygiene helps control caries, high-risk individuals may benefit from oral care products combining antibacterial and remineralizing agents. Bioactive glass (BAG) toothpastes support remineralization and can raise oral pH through ion release; formulations have evolved under different trade names including NovaMin and BioMin. BioMin F contains fluoride and releases ions over prolonged periods, forming fluorapatite; NovaMin (calcium sodium phosphosilicate) rapidly releases calcium, sodium, and phosphate ions to form a calcium phosphate layer. Although many studies have assessed remineralization and sensitivity reduction with these materials, their antimicrobial efficacy against Streptococcus mutans has not been previously tested. This in vitro study aimed to compare the antibacterial effects of BioMin F and NovaMin against Streptococcus mutans versus a commonly used fluoride toothpaste (Signal). The null hypothesis was that all toothpastes would limit Streptococcus mutans growth similarly in vitro.

Prior studies highlight the role of bioactive glasses in dentin/enamel remineralization and potential to elevate pH via calcium and phosphate ion release. BioMin F (fluorine-containing BAG) can form fluorapatite and sustain fluoride release up to 12 hours after brushing, whereas NovaMin (45S5 calcium sodium phosphosilicate) releases ions quickly to form a calcium phosphate layer. Clinical and in vitro studies have shown remineralization benefits and reduced sensitivity with these agents, but direct antimicrobial testing against Streptococcus mutans had not been reported. Additional literature notes that agar diffusion is appropriate for diffusive agents but cannot distinguish bacteriostatic from bactericidal effects. Fluoride exhibits anti-cariogenic activity against S. mutans and can disrupt bacterial metabolism and membranes; crystalline calcium phosphate structures can reduce S. mutans biofilm formation. Manufacturer data suggest BioMin F-derived fluorhydroxyapatite is more acid-resistant than hydroxyapatite formed with NovaMin. Signal contains sodium lauryl sulfate (SLS), which has reported anti-S. mutans properties in vitro.

Ethics: Approved by the Local Research Ethics Committee, Faculty of Dentistry, Damascus University (UDDS-693-07092020/SRC-1450); informed consent obtained; funded by Damascus University. Culture media: Mitis Salivarius Agar with 20% sucrose and 0.2 IU/mL bacitracin was prepared, sterilized (110 °C, 15 psi, 15 min), cooled, supplemented, poured into Petri dishes, and stored inverted to prevent condensation. Isolation of S. mutans: Dental plaque was collected from 10 children (2–6 years, SECC) using sterilized toothpicks from specified tooth surfaces, transferred to saline, homogenized, serially diluted to 10^-5, and plated on Mitis Salivarius Bacitracin agar. Plates incubated at 37 °C, 15% CO2, 72 h. Colonies consistent with S. mutans morphology were confirmed by catalase test (negative), Gram stain (positive), and PCR. Isolates were stored at −80 °C in brain heart infusion medium for later use. Bacterial activation: An isolate was subcultured on Mueller–Hinton medium; a colony was inoculated into brain heart infusion broth and incubated at 37 °C for 24 h. Suspension turbidity was adjusted to 0.5 McFarland (1.5×10^8 CFU/mL) with a nephelometer. Plate preparation: Mueller–Hinton agar was poured into 20 Petri plates (60 mm). Three 9-mm wells (approx. 4 mm deep) were made per plate. A 100 µL aliquot of the standardized S. mutans inoculum was spread uniformly over each plate using a sterile technique and allowed to absorb 20–30 min. Agar diffusion test: Toothpastes tested were BioMin F, NovaMin (Sensodyne), and Signal. Pastes were loaded into sterile syringes and dispensed into designated wells; plates were coded and incubated inverted at 37 °C for 24 h in 15% CO2. Inhibition zones were identified as clear areas around wells and measured in mm with a digital caliper. Statistical analysis: Data analyzed in SPSS v17. Normality was assessed with Shapiro–Wilk. One-way ANOVA was used for intergroup comparisons and Bonferroni for pairwise tests. Significance was set at p < 0.05 (95% confidence).

- N = 20 wells per toothpaste group. After 24 h incubation on Mueller–Hinton agar, inhibition zone diameters differed significantly among groups (one-way ANOVA, p < 0.001). - Mean (± SD; range) inhibition zones: BioMin F: 2.67 ± 0.42 mm (2.0–3.9); Signal: 2.19 ± 0.26 mm (2.0–3.1); NovaMin: 0.39 ± 0.42 mm (0.0–1.0). - Pairwise comparisons (Bonferroni): BioMin F > Signal (p < 0.001); BioMin F > NovaMin (p < 0.001); Signal > NovaMin (p < 0.001). - BioMin F exhibited the greatest antibacterial activity; NovaMin showed minimal inhibition.

The study addressed whether bioactive glass-containing toothpastes differ in antibacterial efficacy against S. mutans. Findings refute the null hypothesis, showing BioMin F significantly outperformed Signal and NovaMin, and Signal outperformed NovaMin. The superiority of BioMin F may be due to its fluoride incorporated within the bioactive glass matrix enabling prolonged, gradual fluoride release and fluorapatite formation, enhancing anti-S. mutans action beyond the shorter-lived effects of soluble NaF (as in NovaMin and Signal). Fluoride can inhibit bacterial metabolism and alter membrane function, while calcium phosphate phases may hinder biofilm formation. Signal’s advantage over NovaMin may relate to sodium lauryl sulfate’s antimicrobial activity. The agar diffusion approach is suitable for diffusive agents but cannot distinguish bacteriostatic versus bactericidal effects and may not fully represent intraoral conditions. Nevertheless, results support the potential role of BioMin F toothpaste as part of preventive strategies for caries risk reduction, particularly in high-risk populations.

After 24 h incubation in Mueller–Hinton medium, BioMin F toothpaste demonstrated superior antibacterial activity against Streptococcus mutans compared with Signal and NovaMin; NovaMin exhibited the lowest effect. These in vitro results suggest BioMin F may be a useful preventive adjunct to reduce caries risk. Future research should evaluate antibacterial efficacy across a broader range of cariogenic species, assess performance under varying pH conditions and media more representative of the oral environment, and test against diverse clinical strains from individual patients.

- Bacterial spectrum: Only Streptococcus mutans was tested; other cariogenic bacteria (e.g., Streptococcus sobrinus, Lactobacillus acidophilus, Lactobacillus rhamnosus) were not assessed due to isolation difficulty and cost. - Test medium and conditions: Antibacterial effects were evaluated only on Mueller–Hinton medium (pH 7.2–7.4); performance in more acidic environments—where fluoride may be more active—was not examined. - Strain representativeness: The bacteria used in Petri dishes did not correspond to separate, patient-specific strains from each child’s plaque, limiting generalizability across diverse clinical isolates. - Methodological constraint: The agar diffusion test assesses diffusion-dependent inhibition zones and cannot differentiate bactericidal from bacteriostatic action, potentially affecting characterization of toothpaste antibacterial properties.