Enamel Surface Alterations after Bleaching Applications: Acetate Peel Technique

Objectives: The aim of this study was to investigate the morphological changes of human enamel after application of different office and home bleaching agents by using the acetate peel technique. Methods: Newly extracted six non-carious maxillary central teeth crowns were vertically separated into two pieces. One separated piece of tooth behaved as control. The specimens were embedded in acrylic blocks leaving labial surface uncovered. Flat labial surfaces were obtained by grinding with different grades of mono-polycrystalline diamond suspension, Struers®. The test groups, according to surface treatments were: Group 1: 16 % carbamide peroxide (Polanight®, SDI) Group 2: 17 % carbamide peroxide (Perfect Bleach®, VOCO) Group 3: 35% hydrogen peroxide (Opalescence Xtra®,ULTRADENT) The carbamide peroxides were applied 6 hours daily and the hydrogen peroxide was applied for 30 min/week, at 37° C, for one week. Following applications, specimens were stored in artificial saliva 18 hours daily, at 37° C. The surfaces were etched by H3PO4 (37%), thoroughly washed and dried then flooded with acetone (99%). A piece of acetate sheet was placed over the surfaces. As the acetone evaporated, a detailed relief of etched surface was transferred to the acetate film and mounted between two pieces of lantern-slide glass. The peels were examined under the transmitted light microscope Results: 35% hydrogen peroxide induced moderate alterations like waviness and erosions on enamel superficial areas. The enamel surface was covered with an amorphous layer obscuring the characteristic perikymata and imbrication lines. Mild surface alterations were seen in carbamide peroxide groups, but they were quite similar to the control group. Conclusions: The exposure to 35% hydrogen peroxide altered enamel superficial morphology than carbamide peroxide.