Effect of Topical Fluoride Solutions on the Enamel Surface as Studied by Scanning Electron Microscopy

The morphological effects of acid pretreatment and topical fluoride applications on enamel was examined using scanning electron microscopy (SEM). Following acid pretreatment of enamel surfaces with phosphoric acid, topical applications of acidulated phosphate fluoride, stannous fluoride, ammonium fluoride, and a sequential acidulated phosphate fluoride and a stannous fluoride solution were performed. The SEM micrographs showed several protective coatings (calcium fluoride and an amorphous layer) formed on the enamel surface. The best results in reducing the porosity and honeycomb etch of the phosphoric acid appear to be obtained in the combined applications of APF and 10% stannous fluoride solutions.