Preventive effect of mouthwash for artificial incipient carious lesions

Abstract

Mouthwashes have become widely used in the home. We investigated their effect on the process of incipient caries formation in vitro. Five commercial mouthwash products (four with fluoride and one without), two fluoride dentifrices, three aqueous sodium fluoride solutions at 150, 300, and 600 ppm, respectively, and distilled water were used. Blocks of enamel, 5mm×5mm, were cut from the labial surface of bovine teeth. After polishing, 3mm×3mm windows were made on the surfaces of the enamel samples using nail varnish. Each enamel sample was immersed in a demineralization solution of CaNO₃, KH₂PO₄ and CH₃COOH at pH 4.6 for 6 hours, then in either a mouthwash or dentifrice solution for 1 minute followed by remineralization in a solution of CaNO₃, KH₂PO₄, KCl and NaC₂H₆ AsO₂ at pH 7.0 for 18 hours. The samples were then placed in either a mouthwash or dentifrice solution for 1 minute. This procedure was repeated for 5 days, followed by treatment with the remineralization solution for 2 days using the pH cycling method to prepare incipient carious lesions. Digital images of the sample surfaces were acquired employing the quantitative light-induced fluorescence (QLF) method, and three analytical parameters : ΔF, area and ΔQ, were measured using accessory analytical software. The sample surfaces with incipient enamel caries were also observed under SEM.
Fluoride mouthwashes significantly inhibited enamel demineralization compared with the non-fluoride group. No significant differences were noted in the parameters of QLF image analysis between the samples treated with fluoride dentifrices and fluoride mouthwashes. The fluoride level in the mouthwashes and dentifrices were significantly correlated with ΔQ, showing that demineralization was inhibited in a manner dependent on the fluoride concentration in the mouthwashes. The SEM images showed crystal structures formed around enamel prisms in the fluoride group. The density of the crystal structure increased as the fluoride level rose, and the production of a calcium fluoride-like substance was also noted. We found that mouthwashes inhibited the incipient caries formation process by remineralization of the enamel through the incorporated fluoride. It was also suggested that mouthwashes and dentifrices with a fluoride level greater than 200ppm effectively inhibit demineralization and subsequent incipient caries formation.