Objectives To test if a novel dual-phase gel system (calcium silicate and phosphate with 1450 ppm F, as NaF/MFP; TG) combined with a toothpaste (calcium silicate and sodium phosphate with 1450 ppm F, as MFP; TG) was able to re-harden previously acid-challenged enamel to a greater extent than other toothpastes. Methods The study consisted of a double-blind, randomised, cross-over design with four 7-day treatment legs. In each leg, subjects wearing a partial denture holding four demineralised enamel specimens (25 min in 0.3% citric acid, pH 3.8) used either the test regimen (TG + TP) or one of the three controls. (placebo TG + TP; Positive Control - placebo TG + marketed 1450 ppm F toothpaste; Negative Control - placebo TG + placebo TP). Enamel specimens were removed after 1, 2, 3 and 7 days. The gel systems were applied once per day for the first three days during which subjects also brushed with the corresponding toothpaste; this was followed by four days use of the toothpastes only. Toothpastes were used in the conventional way brushing twice per day throughout the seven days. The outcome variable was %Surface Microhardness Recovery calculated after three and seven days of in situ treatment. Results The results showed a statistically significant (p < 0.001) re-hardening effect for all treatments compared to pre-treatment hardness. After three days and after seven days of in situ treatment significantly greater hardening (p < 0.05) was found in the samples treated with calcium silicate/phosphate gel system plus calcium silicate/phosphate toothpaste than in the control groups. Conclusions It is concluded that the test regimen based on the novel dual-phase gel system combined with toothpaste was able to re-harden acid-challenged tooth enamel to a greater extent than a normal fluoride toothpaste. Clinical Significance The novel oral care products containing calcium silicate, sodium phosphate salts and fluoride is a new approach to the repair of demineralised enamel.
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