When hypersensitivity was confirmed, desensitising treatment was performed with 2% potassium nitrate (Desensibilize KF 2%, FGM Dentscare Ltda, Joinville, SC, Brazil). The four subjects were instructed to place the desensitizing gel in their tray and wear it for 20 minutes http://www.selleckchem.com/products/INCB18424.html once a day, as recommended by the manufacturer. Surface analysis After detachment from teeth, the specimens were left to dehydrate for 96 hours before being gold sputter-coated to permit analysis in a scanning electron microscope (DSM-940 A, Carl Zeiss, Oberkochen, Germany). Digital SEM photomicrographs were taken at four different areas over the surface of each fragment at 5000x magnification. Enamel and resin surface alterations were classified qualitatively by increasing order of scores ranging from 0 (no observable alterations) to 4 (heavy erosion with deep depressions).

Prior to blind analysis of the 160 images, a single examiner was calibrated by viewing 30 additional SEM micrographs. A second assessment was repeated 4 weeks after the first evaluation, and the data obtained were considered as a whole for statistical comparison. Statistical analysis Statistical differences between the experimental and appropriate control groups were executed with the Mann-Whitney Test adjusted to the 95% confidence interval. The intra-observer agreement was determined using Cohen��s Kappa statistic. Statistical analyses were performed with SPSS software v.11.0 for Windows (SPSS Inc., Chicago, IL, USA). RESULTS Representative SEM images are shown in Figures 1�C4, and the results of the Mann-Whitney test are presented in Table 1.

Figure 1. Representative SEM micrograph of bleached enamel at original magnification 5000x. Figure 4. Representative SEM micrograph of unbleached resin composite at original magnification 5000x. Table 1. Median values and ranges of scores attributed to enamel and resin composite micrographs Following application of 16% carbamide peroxide, the enamel surface in the experimental group exhibited extensive mild erosion with shallow depressions and destruction of interprismatic matrix. This appearance differed significantly from that of non-bleached enamel fragments, which exhibited a smooth and amorphous aspect. The bleached composite resin specimens displayed a flat appearance, with slight erosion and some striation due to the grinding procedure.

This appearance was statistically similar to that observed in the control group (P<.05). Intra-observer agreement was 0.89. DISCUSSION This study was the first to adhere human enamel and resin fragments to the buccal side of regular teeth to reproduce, as closely as possible, an actual home-bleaching situation. This Entinostat manoeuvre permitted controlled and continuous exposure of specimens to saliva, beverages and oral hygiene habits, a procedure completely different from prior investigations in which removable appliances were adopted to carry the specimens.