Evaluation of antibacterial properties of fluoride-containing mouth rinses differing in their acidic compound using a Streptococcus mutans biofilm

Abstract

This in vitro study assessed the antibacterial effect on Streptococcus mutans biofilms of mouth rinses with 700 ppm F- (derived from NaF) that differed only in their acid compounds (malic, citric, tartaric, fumaric, hydrochloric, phosphoric, and lactic acid) used to adjust pH.

S. mutans (ATCC™ 25175) was grown for 22 h at 37°C, harvested, resuspended in simulated body fluid and biofilm formation followed for 24 h at 37°C. Thereafter, biofilms were treated with experimental rinses for 30 s and placed in TAM48 isothermal microcalorimeter at 37°C for 72 h. Applying Gompertz growth model the parameters lag time and growth rate were determined from heat flow curves; additionally, reduction of active biofilms was calculated. Moreover, samples were live/dead-stained and analysed by confocal scanning microscopy.

All mouth rinses were showing statistically significant lag time and reduction of active biofilm (p < 0.05, A 19.1 ± 2.3 h and 58.5 ± 7.7%, B 15.5 ± 1.1 h and 41.9 ± 5.3%, C 17.6 ± 1.9 h and 53.1 ± 7.5%, D 18.4 ± 2.4 h and 55.8 ± 8.8%, E 20.2 ± 3.3 h and 61.5 ± 10.0%, F 20.2 ± 3.0 h and 61.6 ± 9.3%, and G 18.3 ± 2.5 h and 55.3 ± 8.9%). Interestingly, there were no differences found between the treated groups (p > 0.05, A 0.064 ± 0.004 1/h, B 0.063 ± 0.005 1/h, C 0.065 ± 0.004 1/h, D 0.067 ± 0.004 1/h, E 0.066 ± 0.006 1/h, F 0.067 ± 0.004 1/h, G 0.066 ± 0.006 1/h) for the maximum growth rate. Vitality staining supported these findings.

The present investigation demonstrates that the type of acid compounds used to produce the rinses did not show any negative effect on the antimicrobial properties of the tested products as all of them exhibited a similar efficacy against S. mutans biofilms.