An atomic force microscopy study on the effect of bleaching agents on enamel surface

Objectives: The aim of the present study was to evaluate the effect of thre e peroxide-containing bleaching agents, Opalescence, Nite White and a 30% h ydrogen peroxide solution, on enamel surfaces using Atomic Force Microscopy (AFM). Methods: Fifteen non-carious human incisors (ten maxillary and five mandibu lar, extracted for periodontal reasons) were used. The teeth were divided r andomly into three groups of five, according to the bleaching agents. The l abial surface of each tooth was imaged by AFM before and after treatment. E ach bleaching agent was applied for a total of 28 h (in individual 4 h trea tments). The specimens were examined only after 28 h of treatment. Results: On comparing the AFM images of untreated and treated enamel, surfa ce alterations were observed after 28 h of treatment with Opalescence, Nite White and 30% hydrogen peroxide solution. Several grooves present in the e namel surface of untreated teeth became deeper after the bleaching procedur e. The depths of the grooves increased in each case. The increase in the de pth of grooves was more pronounced in the case of the 30% H2O2 solution. Conclusion: Home-use bleaching agents are capable of causing enamel surface alterations. It is hypothesized that the peroxide-containing bleaching age nts affect the organic phase of enamel. Peroxides can affect not only the s urface but also the inner structure of enamel. As a result of its low molec ular weight, hydrogen peroxide can penetrate into the enamel. Thus, inner o xidative effects are more likely to occur in the subsurface enamel where mo re organic material is present and oxidation is capable of altering the out er enamel and the surface. (C) 1999 Elsevier Science Ltd, All rights reserv ed.