Under acidic conditions some bacterial species, e.g. S. mutans, can alter their physiology and induce an acid tolerance response (ATR) in order to survive the low pH that arises in dental plaque biofilms when carbohydrates are metabolised. It has been reported that this induction can be prevented by the presence of fluoride during the adaptation phase, and this study was performed to evaluate if similar effects will be obtained with delmopinol and combinations of delmopinol and fluoride.
Methods:
Monocultures (S. mutans) and pooled human plaque samples were tested in two flow cell models. Studies on the effect of delmopinol on ATR development were performed in flow cells consisting of two parallel glass slides separated by rubber spaces. In studies aimed to evaluate the combined effect of delmopinol and fluoride the Ibidi micro-flow cell system was used. The samples were subjected to different acid adaptive tests and bacterial viability was assessed by fluorescence microscopy using the LIVE/DEAD BacLight viability kit.
Results:
It was found that delmopinol at sublethal concentrations inhibits development of ATR in biofilms of S. mutans and that delmopinol and fluoride do not interfere with respect to their inhibition of ATR development. Instead their action seems to be additive and the inhibitory effect was obtained at very low concentrations of the compounds. This was true for both the mutans as well as the plaque sample biofilms.
Conclusions:
·Delmopinol strongly affects the ability of Streptococcus mutans and plaque bacteria to adapt to acidic conditions.
·The action of delmopinol and fluoride is additive and the ATR-inhibitory effect is obtained at low doses of the compounds.
·This study suggests that a combination of delmopinol and fluoride should be valuable for caries prevention.