A scanning electron microscopic study of enamel surfaces treated with topical fluoride agents in vivo.

The morphological appearance of human enamel treated with topical fluoride (F) agents was studied. Maxillary acrylic appliances carrying the enamel sections were worn for 24 h following 5-min application of neutral NaF gel-drops, APF gel and Duraphat varnish. All F treatment induced surface coatings composed of globules, suggestive of CaF2. The sizes of the globules varied according to the F agents and, in general, were less than 1 micron in diameter. The globules formed following neutral NaF gel-drops and APF were spherical; while those produced by Duraphat were flattened, forming a sheet-like deposit. Irregular masses of organic-like material were seen on F- untreated enamel, which were exposed to the oral environment for 24 h (controls). The prolonged retention of a F-rich surface coating may act as a reservoir of F supplement to the enamel microenvironment, which thus contributes to remineralization.