The effects of fluoride and mineralising treatments on plaque microcosm Ca, P and F, pH responses and cariogenicity.

Objective: To investigate the effects of fluoride (F), calcium-phosphate-monofluorophosphate-urea (CPMU) mineralising solution, and casein on plaque pH and calcium (Ca), phosphate (P) and F content, and the ability of plaque to induce carious lesions in enamel.

Methods: Plaque microcosms were cultured in cariogenic growth conditions on enamel specimens for 28d in a "multiplaque artificial mouth". The plaques were supplied 5 times daily with 10% sucrose (1.5 ml over 6 min) over a 12h period followed by a 12h rest period. Duplicate plaques were pulsed with 0, 1000, 3000 and 5000 ppm F (1.5 ml over 6 min) or 2% w/v casein (1.25 ml over 30 min) twice daily. One of each pair was also pulsed with CPMU (1.5 ml over 6 min). Plaque pH was monitored during growth. After 28 days' culture, plaque Ca, P and F levels were quantified and lesion depth in enamel was measured by backscattered electron SEM.

Results: F pulses raised the plaque pH, which was otherwise below 4 during sucrose pulsing, while CPMU hastened and raised the recovery pH. Plaque Ca, P and F levels substantially increased with increasing concentrations of applied F, particularly in the presence of CPMU (P < 0.01). In the absence of either F or CPMU, enamel lesions were formed with extensive enamel loss.

Conclusions: CPMU and F supplied to plaque microcosms substantially reduce plaque cariogenicity to enamel under highly cariogenic experimental conditions. This was associated with an increase in plaque pH, plaque F and Ca levels.