Previous studies have concluded that copper might inhibit enamel demineralization in vitro. Our aim was to assess the effect of copper (Cu2+), with and without amine fluoride, on human dental enamel under cariogenic challenge in situ. In a double-blind randomized four-leg crossover trial, 14 individuals wore a removable appliance containing 2 enamel slabs, 1 containing an artificial caries lesion. During each leg, the appliance was exposed twice daily to one of the test solutions: 1.25 mM CuSO4, amine fluoride (250 ppm F), copper and amine fluoride combined, or a placebo (water). A cariogenic challenge was provided in all cases by 5 daily exposures to 10% sucrose. Slabs were assessed before and after 21 days' exposure by Knoop microhardness and transverse microradiography. Significantly less demineralization was observed with Cu2+ and fluoride in combination than with fluoride treatment alone (p < 0.05), whereas copper alone had no significant protective effect.

An increasing interest in dental erosion as a clinical and scientific phenomenon has led to concerted efforts to identify agents which might protect against erosion. In this study, nanoindentation was used to investigate inhibition of erosive enamel demineralisation over time scales with direct clinical relevance. Nanohardness of polished human enamel specimens (n = 8 per group) was measured at baseline (B), after demineralisation (D1: citric acid, 0.3% w/v, pH3.20, 20s), after treatment (T), and after a second demineralisation (D2: as above). Data were analysed using repeated measures ANOVA. All specimens exhibited a similar reduction in nanohardness B-D1 in the range 35.2–39.5%. The positive control solution (saturated hydroxyapatite solution) and 4500 mg/L fluoride as NaF significantly increased nanohardness D1-T by 19.9% and 24.1%, respectively, whereas 1400 mg/L fluoride as NaF, casein phosphopeptide-amorphous calcium phosphate mousse and negative control (deionised water) had no significant effect. Nanohardness at D2 was indistinguishable for all groups, with total reduction in nanohardness B-D2 of 31.6% (4500 mg/L fluoride), 35.2% (positive control), 39.9% (1400 mg/L fluoride), 42.4% (negative control), and 43.7% (CPP-ACP product). In summary, 4500 mg/L fluoride significantly increased the nanohardness of previously demineralised enamel and resulted in the smallest total reduction in nanohardness but there were few statistically significant differences among the groups.

Objectives:  To compare the effect of brushing versus dipping using three different concentrations of fluoridated toothpastes on enamel erosion in vitro using surface profilometry. Methods:  In a randomised, blinded experiment six groups of seven enamel slabs each were cut and mounted into resin blocks, ground and checked for surface flatness using a scanning profilometer (Scantron Proscan 2000). Each slabs’ surface was covered with nail varnish except for a small window (1 x 2 mm). Each group was immersed under static conditions for 2 minutes, five times daily in fresh 200 ml aliquots of citric acid 0.3% (pH = 3.6). In addition, three groups were immersed in three different fluoridated toothpastes (0 ppm F, 1100 ppm F, or 1450 ppm F) twice daily morning and evening for 2 minutes each time. The other three groups were brushed using the same toothpastes twice daily for 2 minutes each time. The total cycling period lasted 16 days during which the slabs were incubated overnight and between erosive challenges in artificial saliva at 37oC. A 60‐minute gap was left between daytime immersions. Before and after dipping in the erosive solutions the slabs were rinsed with de‐ionised water. After the cycling period, the slabs were analysed with the scanning profilometer to measure the amount of surface loss at day 4, 8, 12, and 16. Results:  Surface loss ± SD of enamel at day 16 caused by citric acid combined with dipping using non‐fluoridated toothpaste was 61.19 ± 8.50 μm, 1100 ppm F was 43.44 ± 10.94 μm or 1450 ppm F was 34.98 ± 4.29 μm. Surface Loss ± SD of enamel at day 16 caused by citric acid combined with brushing using 0 ppm F, 1100 ppm F, or 1450 ppm F toothpastes was 75.62 ±10.64, 63.51 ± 5.27 and 48.94 ± 13.67 μm, respectively. Conclusion:  Enamel erosion was increased significantly (CI 95%) using brushing with toothpastes compared to dipping. In addition, enamel erosion showed a dose‐response to fluoridated toothpastes. Acknowledgment:  This project was supported by GlaxoSmithKline.