Fluoride Effects on Dentine Surface Loss under Erosive Cycling Conditions

Objectives: To compare the effect of 5 different concentrations of sodium fluoride in matched toothpastes on surface loss of human dentine in vitro using an erosive cycling technique.

Methods: Five groups of eight dentine slabs were cut and mounted into resin blocks, ground and checked for surface flatness using a scanning profilometer (Scantron Proscan 2000). The surface of each slab was covered with nail varnish except for a small window (1X2 mm). Using a randomised, blinded study design slabs were immersed for 2 minutes, five times daily in fresh 200 ml aliquots of 0.3% citric acid (pH=3.6). In addition, each group was immersed in one of five (0, 250, 500, 1150, or 1450 ppm fluoride [as NaF]) toothpaste slurries twice daily, morning and evening, for 2 minutes each time. Total cycling period lasted 21 days during which slabs were incubated overnight and between erosive challenges in artificial saliva (37oC). A sixty minute gap was left between day time immersions. Slabs were analysed with scanning profilometry to measure the amount of surface loss at day 7, 14, and 21.

Results: Significant bulk tissue loss was observed across all treatment groups, at all timepoints. Surface loss ± SD of dentine at day 21 after cycling with 0, 250, 500, 1150, or 1450 ppm NaF toothpastes was 41.2± 6.4µm, 28.0± 1.8µm, 26.6± 4.6µm, 24.3± 2.9µm and 24.0± 2.2µm respectively.

Conclusion: Dentine surface loss was reduced significantly (p ≤ 0.05) with fluoride concentrations in toothpaste over 250 ppm. At day 21 the 1450ppm and 1100ppm F pastes were statistically superior to the 250ppm F paste. No other significant product differences were observed between fluoridated pastes.