Effect of high concentrated fluoride on the surface layer of enamel subsurface lesion

Abstract

We studied the effect of high concentrated fluoride on enamel subsurface lesions. Enamel specimens 3mm in diameter were prepared from extracted human incisors using a hollow core drill. The specimens were highly polished and subsurface lesions were produced by immersion in a demineralizing solution for 24 hours. The specimens were treated with acid phosphate fluoride (APF) solution and then washed in 1 M KOH solution. The samples were analyzed by atomic force microscope (AFM), electron spectroscope for chemical analysis (ESCA), SEM and x-ray microanalyzer (XMA). We found that treatment with a high concentration of APF improved the enamel to be calcium fluoride like-materials at only to a depth 5 μm from the surface, but did not alter the entire subsurface lesion. When this improvement was washed in KOH, calcium fluoride like-materials were eliminated from the surface. This elimination may make the subsurface lesion decrease acid resistance. This suggests that it is necessary a fluoride treatment program to aid in maintaining calcium fluoride like-materials formed at the surface layer of the subsurface lesion.