Effect of acid-etching on fluoride-treated caries-like lesions of enamel: a SEM study

Etching patterns by 20 percent phosphoric acid on caries-like lesions of enamel (white spot) untreated and treated with 0.4 APF were studied at 30, 60, 120 seconds of etch-times using the Scanning Electron Microscope (SEM). The surface topography of acid-etched teeth varied according to the etch time. Acid etching of caries-like lesions treated with fluoride showed etching patterns similar to sound enamel. Based on Silverstone's classification, thirty seconds etch-time produced type III pattern of surface morphology, while type I and type II were observed with 60 and 120 seconds of etch time. Fluoride treated lesions showed increased porosity and in addition to a surface coating of numerous small globules of calcium fluoride. Low level of topical fluoride before sealant application should be beneficial, since this allows a more rapid rate and increased degree of remineralization and possible arrest in the progress of caries lesions.