Stannous Source in Toothpastes Leads to Differences in Their Antimicrobial Efficacy

Abstract

Purpose: The aim of this in-vitro study was to investigate the antimicrobial efficacy of identical experimental toothpastes with different stannous sources.

Materials and methods: Streptococcus mutans biofilms were grown on protein-coated glass disks in static conditions for 24 h and thereafter exposed to toothpaste slurries or physiological saline (negative control; n = 15) for 30 s. Four experimental toothpastes were applied in this study, containing either stannous chloride (SnCl2; B: 3500 ppm Sn2+, and D: 3600 ppm Sn2+) or stannous fluoride (SnF2; C: 3500 ppm Sn2+, and E: 3600 ppm Sn2+). Marketed toothpaste meridol® (A: 3300 ppm SnF2) served as control. All five toothpastes contained amine fluoride (AmF). The biofilms were placed on agar surface and their metabolic activity was assessed by isothermal microcalorimetry over 96 h. The heat flow data was analysed for growth rate and lag time using grofit package in software R. Additionally, reduction of active biofilm compared to untreated control was calculated.

Results: All toothpastes significantly prolong the lag time of treated biofilms in comparison to negative control (p < 0.05). Toothpastes containing SnF2 (C and E) prolonged the lag time statistically significantly compared to toothpastes containing SnCl2 (B and D) (p < 0.05). The maximum growth rate was statistically significantly reduced by all tested toothpastes compared to the untreated control group (p < 0.05). Toothpastes containing SnF2 (A, C and E) reached 59.9 ± 7.8, 61.9 ± 7.7, and 55.6 ± 7.0% reduction of active biofilm, respectively. Thus, they exhibit statistically significantly better results than toothpastes B (52.9 ± 9.9%) and D (44.7 ± 7.6%). Toothpaste D, which contains a slightly higher concentration of Sn2+, was the least effective in reducing active biofilm.

Conclusion: The toothpastes containing SnF2 combined with AmF had the highest antimicrobial efficacy in this study.

Keywords: antimicrobial; biofilm; caries; stannous chloride; stannous fluoride; toothpaste.

Fig 1

Flow diagram illustrating the main steps of the experiment: (1) biofilm formation on salivary-protein-coated disks; (2) exposure to toothpaste slurries; (3) measurement of metabolic activity with isothermal microcalorimetry (IMC); (4) heatflow data of IMC; (5) analysis of IMC data to assess growth parameters (lag time and growth rate) of the biofilms.

Fig 2

Five toothpastes (A-E) which differ in their stannous source were examined for their antimicrobial properties. Three different parameters were assessed from IMC data: (A) lag time in h, (B) maximum growth rate in 1/h, and (C) reduction of active biofilm in % compared to untreated control biofilm. Significant differences between groups are indicated with asterisks (* p < 0.05, ** p < 0.01, **** p < 0.001).