Mineral ions in the fluid of biofilms formed on enamel and dentine shortly after sugar challenge.

To test the effect of distinct solubilities of dentine and enamel on mineral ion concentration in the biofilm fluid during a sugar-induced pH drop, dental biofilms were formed in situ for 4 days on acrylic (control), dentine or enamel. On the 5th day, they were treated with water (control) or 20% glucose and collected 5 min later. Significantly lower pH values and higher calcium concentrations were found in the biofilm fluid after glucose exposure, without significant differences among the three substrates. During pH drop, biofilm reservoirs release calcium to the fluid, masking the differential solubility between enamel and dentine.

Low-fluoride dentifrice and the effect of postbrushing rinsing on fluoride availability in saliva.

AIM: Post-brushing water rinsing may reduce the risk of fluoride (F) ingestion from dentifrice, however the decreased salivary F bioavailability may compromise any consequent anticaries benefits. As the use of low-F concentration dentifrices is still a matter of debate, a comparison was made between the salivary F bioavailability after brushing with a conventional F dentifrice followed by a water rinse and after brushing with a low-F dentifrice without post-brushing rinse. STUDY DESIGN AND METHODS: In a crossover, blind study, F concentration in saliva of 5 adult volunteers was determined after brushing with a low-F dentifrice (500 microg F/g) or with a conventional F concentration dentifrice (1100 microg F/g), followed or not by a 15-mL water rinse. RESULTS: Salivary F bioavailability was reduced by 2.5 times when a water rinse was used (p<0.05), irrespective of dentifrice concentration, and it was 2 times lower for the low-F dentifrice (p<0.05). The salivary F bioavailability was similar when the low-F dentifrice was used without post-brushing rinse and the conventional F dentifrice was followed by a rinse (p>0.05). CONCLUSION: Habits of post-brushing rinse should be taken into account on the recommendation of dentifrice use by young children, considering the risks and benefits balance of F use.

Ca, Pi, and F in the fluid of biofilm formed under sucrose.

Calcium (Ca), inorganic phosphorus (P(i)), and fluoride (F) concentrations are low in the whole plaque biofilm formed under exposure to sucrose. It was hypothesized that this would be reflected in the biofilm fluid, where these low values should greatly influence the de/remineralization process. Dental biofilms were formed in situ over enamel blocks mounted in palatal appliances and exposed 8 times/day to distilled water, glucose+fructose, or sucrose solutions for 14 days. While Ca, P(i), and F concentrations in the whole biofilms were significantly lower in the glucose+fructose and sucrose groups, no effect on biofilm fluid was observed, even after a cariogenic challenge. An increase in whole biofilm mineral ions was observed 24 hrs after the carbohydrate treatments were suspended, but this effect was also not observed in the fluid. These results suggest that there is a homeostatic mechanism that maintains biofilm fluid mineral ion concentration, regardless of its total concentration in the whole biofilm.