Plaque microcosm mineralization and fluoride: effects on enamel lesion formation

Objective: To investigate enamel lesions developed by plaque microcosms pulsed with high fluoride, with and without exposure to pH 5.0 calcium phosphate-monofluorophosphate urea (CPMU) mineralising solution. Methods: Ten microcosm biofilms were grown for 28 d on prepared enamel blocks in the Multiplaque Artificial Mouth and pulsed with 10% sucrose 5 times in 12 h (3 h intervals), followed by 12 h with no sucrose. Duplicate plaques were pulsed for 6min with 0, 1000, 3000 and 5000ppm fluoride, or 2% casein for 30 min, twice daily. To one of each pair, CPMU was also pulsed, twice daily. On day 28, the enamel blocks were axially sectioned and fine polished, and lesion appearance and mechanical properties investigated using an Ultra Micro Indentation System. Results: Enamel exposed to sucrose only, or with casein pulsing, had substantial enamel loss: lesion depth (SD) 568µm (94.5µm) and 407.3 (6.3µm) respectively. CPMU alone did not completely halt but decreased demineralisation: lesion depth 125µm (4.4 µm), with hardness ranging from 0.89 – 3.57GPa, and elastic modulus from 18.8 – 58.4GPa. Casein enhanced CPMU protection against the sucrose-induced cariogenic attack: lesion depth about 10µm. Slight superficial demineralisation occurred with 1000ppm fluoride, but 3000 and 5000ppm fluoride virtually abolished lesion formation, even in the absence of CPMU. Conclusion: Under a very cariogenic sucrose regime, pulsing with CPMU two times a day considerably reduced lesion formation in enamel, but not as effectively as short-term exposure to high concentration fluoride.