Microbial approaches for the assessment of toothpaste efficacy against
oral species -- a method comparison
Abstract
Antibacterial properties of toothpastes enable chemical plaque control
in limited-access tooth regions that are mechanically not sufficiently
reached by toothbrushes. Therefore, this study aimed to compare
different microbial methods to assess antimicrobial toothpaste
properties and evaluate different toothpastes in terms of their
antibacterial efficacy against different oral microorganisms in vitro.
Six toothpaste suspensions with varying antibacterial supplements were
applied to a multi-species biofilm model (Actinomyces oris, Candida
albicans, Fusobacterium nucleatum, Streptococcus oralis, Streptococcus
mutans) as well as to each microorganism. A culture method was used to
assess the anti-biofilm effects and two different agar diffusion assays
were performed for testing the antimicrobial effect on each
microorganism. The measurements of the culture and diffusion analyses
were statistically normalized and compared and toothpastes were ranked
according to their antimicrobial efficacy. The results of both agar
diffusion assays showed a high correlation across all tested species
(Spearman correlation coefficients ρs > 0.95). The results
of the multi-species biofilm model, however, substantially differed in
its assessment of antibacterial properties (ρs ranging from 0.22 to
0.87), compared to the results of both diffusion assays. Toothpastes
with amine fluoride with and without stannous fluoride, and triclosan
resulted in the highest antimicrobial efficacy, while activated carbon
supplements were comparable to the negative control NaCl. The
appropriate selection of a broad range of oral microorganisms seems
crucial when testing the chemical impact of toothpastes and toothpaste
supplements.