The effect of delmopinol and fluoride on acid adaptation and acid production in dental plaque biofilms.

OBJECTIVE: To investigate the effect of delmopinol and fluoride alone or in combination on acid adaptation and acid production in plaque biofilm bacteria in vitro. DESIGN: The effect of delmopinol and fluoride on acid adaptation was tested by exposing the biofilm bacteria, grown in a mini-flow cell system under static conditions, to pH 5.5 overnight in the presence of 0.16 mM delmopinol, 1 mF NaF or a combination of both. The following day, acid adaptation was evaluated by exposing the cells to an acid challenge for 2h at a pH known to kill non-adapted cells (pH 2.5). The cells were stained using LIVE/DEAD BacLight Viability stain and the number of viable (acid tolerant) cells was determined using confocal scanning laser microscopy. Control cells were treated in the same manner but without the exposure to delmopinol or fluoride. How delmopinol and fluoride affected acid production was assessed by measuring the pH-drop after glucose pulsing in the presence of delmopinol and/or different concentrations of fluoride. RESULTS: Fluoride alone or in combination with delmopinol affected the acid adaptation and significantly reduced the acid tolerance of the plaque biofilm. This effect was more pronounced when the two compounds were combined. Delmopinol alone did not affect acid adaptation. A combination of delmopinol and fluoride also reduced acid production at concentrations where neither of the compounds in isolation had an effect. CONCLUSION: Fluoride and delmopinol can work synergistically to affect acid adaptation and acid production in plaque biofilm bacteria.