Protective effect of hexetidine against in vitro bacterial demineralisation of bovine enamel and dentin in the presence of fluoride.

Bovine enamel and dentin specimens were overlaid with acidogenic Streptococcus mutans suspensions in agarose. In this model, the minimal demineralisation-inhibiting concentrations (MDIC) of hexetidine was determined in the presence of fluoride. A commercially available mouthwash containing 0.1% (2.9 mmol/l) hexetidine was diluted serially and added to the bacterial suspensions together with 0, 5.3, or 26.3 mumol/l fluoride (NaF). After 22 h of incubation at 37 degrees C the bacterial suspensions were removed and assessed for calcium and lactate. The results showed significant inhibitory effects of hexetidine on the demineralisation of the enamel specimens with a MDIC between 15 and 31 mumol/l hexetidine. In the presence of fluoride, approximately fourfold higher concentrations of hexetidine were needed for a significant additional protection of the enamel. No synergistic effect between hexetidine and fluoride was observed. For the demineralisation of the dentin specimens, the MDIC of hexetidine had a value between 31 and 61 mumol/l. At both these concentrations the dentin specimens were relatively less protected in the presence than in the absence of fluoride, and some synergistic effect between hexeditine and fluoride was observed.