Abstract

Robert L. Karlinsey*, Allen C. Mackey, Emily R. Walker, Katherine E. Frederick and Christabel X. Fowler

The anti-erosion effects of 225 ppm fluoride plus an innovative form of tricalcium phosphate (TCP-Si-Ur) relative to 225 ppm fluoride were investigated using a pH cycling model comprising treatment, saliva and acid challenge periods. Polished bovine enamel specimens were initially softened in 1% citric acid (pH = 3.8) and stratified (N = 10) into the following groups according to their Vickers microhardness: water, 225 ppm fluoride and 225 ppm fluoride containing 20, 40, or 80 ppm TCP-Si-Ur. The cycling regimen consisted of three two-minute treatment periods and five two-minute acid challenges (1% citric acid, pH = 3.8) per day for a total of 20 days. Surface microhardness measurements were made at 10 and 20 days. After 10 days, statistical differences (t-tests, p < 0.05) only existed between water and each of the four fluoride-containing groups. After 20 days, significant differences were observed among the fluoride-containing groups, with fluoride plus 20 ppm TCP-Si-Ur providing significant surface strengthening relative to fluoride alone. Cross-sectional microhardness measurements revealed distinctly different strength profiles and infrared spectroscopy was employed to probe possible changes in enamel microstructure. Collectively, our results indicate a synergistic effect can be produced when TCP-Si-Ur is combined with fluoride and administered to eroded enamel.