A simulated oral hygiene model to determine the efficacy of repeated exposure of amine oxide on the viability of Streptococcus mutans biofilms

The use of biocide in oral care products is important for controlling microbial pathogens. However, the use of biofilm tests that investigate repeated exposure to biocide, to mimic in situ treatment, has rarely been reported in the literature. The present study describes the application of a biofilm-based efficacy protocol, for testing the effect of repeated exposure to antimicrobials on biofilm, in an attempt to mimic oral care regimens. The activity of different treatment regimens, including repeated exposure to amine oxide (AO; C10-C16-alkyldimethyl N-oxides; 1.1% v/v), was conducted against 16-h Streptococcus mutans biofilms grown on hydroxyapatite disks. Single exposure to AO alone produced a 3 log10 reduction in microbial count, but when combined with mechanical removal, a 5 log10 reduction in microbial count was observed. Treatments incorporating repeated exposure to AO reduced the microbial count below the level of detection, even when exposure to AO was interspersed with recovery periods. The presence of organic load produced an additional 2 log10 reduction in the microbial count. This study showed that the application of a biofilm-based efficacy protocol to mimic oral care regimens allowed the reproducible testing of repeated antimicrobial exposures against bacterial biofilm. In addition, AO was confirmed to be an excellent biocide for eliminating S. mutans biofilms and could therefore be beneficial in oral care formulations.