Sucrose Exposure and pH, Calcium and Fluoride in Biofilm Fluid

Objectives: The composition of dental biofilm changes according to frequency of sucrose exposure but there are very few studies about this effect on pH of biofilm fluid, and on Ca and F concentration. We assessed the relationship between pH, Ca and F on resting biofilm fluid upon exposure to sucrose at 2 daily frequencies and to rinses with increasing F concentrations.
Methods: In a double-blind in situ study, 9 volunteers wore palatal appliances containing enamel slabs, covered by a plastic mesh to allow biofilm accumulation, which were exposed to 20% sucrose 3 or 8x/day. Twice a day, the volunteers used mouthrinses containing 0, 250 or 1,000 ppm F, as NaF. In the morning of the 15th day, after 10 h of the last fluoride rinse, dental biofilm formed on the slabs was collected and its fluid was extracted to analyze pH, ionic calcium (Ca⁺⁺) and fluoride concentration, using micro techniques.
Results: Increasing the frequency of sucrose exposure from 3 to 8x/day (paired tests) resulted in a pH reduction from 6.3±0.7 to 5.8±0.7 (p=0.0003) and increased calcium concentration in the biofilm fluid from 1.5±1.2 to 2.3±1.9 mM (p=0.0007), while the F concentration was not altered (p=0.583). Upon increasing fluoride concentrations in the mouthrinses (ANOVA followed by Tukey test), baseline F concentration increased (p=0.0016) (3.9±2.5; 38.3±15.7 and 468.7±357.3 for groups 0, 250 and 100 ppm F, respectively), but pH and Ca⁺⁺ concentration in the biofilm fluid were not different (p=0.549 and 0.386, respectively). A strong negative correlation (r=-0.86; p<0.0001) was observed between pH and Ca in the biofilm fluid, but not between pH and fluoride (p=0.9262) or Ca and fluoride (p=0.2729).
Conclusions: The results suggest that higher frequencies of sucrose exposure reduce biofilm fluid baseline pH and increases Ca concentration, whereas the change in F concentration in the fluid is dependent on fluoride exposure.