Acid etching in bleached enamel

ABSTRACT

The purpose of this "in vitro" study was to evaluate the effect of a 10 per cent carbamide peroxide bleaching agent (Opalescence) on the enamel surface of human teeth regarding the morphology of bleached enamel to acid etching. Five freshly extracted third molars were sectioned in quarters mesio-distally and then lingo-buccally. All surfaces except the enamel were sealed with nail varnish. From each tooth, one quarter (group 1) was treated for 12 hours with a bleaching agent and the other 12 hours with artificial saliva during 20 days (240 hours of bleaching treatment). Another quarter (group 2) was submitted to the same protocol but after bleaching treatment it remained in distilled water for 12 hours. The other two quarters were used as controls and one stayed all the time in artificial saliva (group 3) and the other (group 4) all the time in distilled water. All samples were then rinsed and acid etched for 15 seconds with 37 per cent phosphoric acid. After the conditioning all the treated enamel surfaces were sputter-coated and examined under a scanning electron microscope for differences in surface morphology. When bleached enamel was acid etched the intercrystalline spaces were enlarged. Comparing saliva-treated enamel with water-treated enamel it is possible to see that these spaces are smaller when saliva is used, suggesting a mineralizing action in saliva. The pattern of enamel conditioning was the same as non bleachead enamel reported in the literature