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Effect of Bleaching Agents on the Hardness and Morphology of Enamel
Author(s) -
LOPES GUILHERME CARPENA,
BONISSONI LEANDRO,
BARATIERI LUIZ NARCISO,
VIEIRA LUIZ CLÓVIS C.,
MONTEIRO SYLVIO
Publication year - 2002
Publication title -
journal of esthetic and restorative dentistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.919
H-Index - 60
eISSN - 1708-8240
pISSN - 1496-4155
DOI - 10.1111/j.1708-8240.2002.tb00144.x
Subject(s) - opalescence , hydrogen peroxide , bleach , enamel paint , sandpaper , carbamide peroxide , molar , dentistry , acrylic resin , saliva , nuclear chemistry , chemistry , tooth whitening , materials science , medicine , composite material , biochemistry , physics , organic chemistry , quantum mechanics , coating
Purpose: The goal of the present laboratory study was to analyze the effect of two home bleaching agents (Opalescence 10%, Ultradent, and Hi‐Lite II, Shofu) as well as the separate solutions of 10% carbamide peroxide primary components (3% hydrogen peroxide and 7% urea) on enamel microhardness and surface morphology. Materials and Methods: Thirty human molars stored in water for no longer than 3 months were selected. Their facial and lingual surfaces were embedded in acrylic resin, and the specimens were polished with up to 600‐grit sandpaper. The 30 molar sections were divided into five groups as per treatment modality (n = 6); group 1, 10% carbamide peroxide bleach with carbopol (Opalescence, Ultradent); group 2, oxygen‐free gel bleach (Hydroxylite, Hi‐Lite II, Shofu); group 3, 3% hydrogen peroxide with carbopol (Dermus Pharmacy, Florianopolis, SC, Brazil); group 4, 7% urea treatment (Dermus Pharmacy); and control, group 5, artificial saliva (Dermus Pharmacy). Prior to treatment, six indentations (Vickers) were made on each of the six surfaces in each group under a load of 100 g for 30 seconds. Bleaching procedure was conducted for 3 hours per day for 2 weeks, the control group excepted. Following each bleaching session, the specimens were washed with deionized water and kept in artificial saliva at 37°C, this solution being changed daily. Pre‐ and post‐treatment microhardness data were analyzed using a two‐way analysis of variance. In a similar way, 30 other specimens underwent the same procedures. After the bleaching period, the samples were observed under the scanning electron microscope. Results: Specimens submitted to bleaching treatment with 3% hydrogen peroxide gel as described in this study showed a significant reduction of surface microhardness (p < .0001). The other treatment modalities had no effect on surface microhardness. No morphologic alterations were observed on enamel submitted to bleaching gel of 10% carbamide peroxide (Opalescence), oxygen‐free gel (Hi‐Lite II, Shofu), or 7% urea solution compared with the control (artificial saliva). However, the specimens bleached for 3 hours per day for 2 weeks with 3% hydrogen peroxide gel presented areas of mild erosion. The effect, nevertheless, was not uniform, occurring with varying intensity on all samples of enamel bleached with 3% hydrogen peroxide. CLINICAL SIGNIFICANCE Bleaching treatment conducted with two home bleaching agents (Opalescence 10%, Ultradent, and Hi‐Lite 11, Shofu) had no adverse effects on enamel microhardness or on surface morphology. Bleaching with 3% hydrogen peroxide can have a negative effect on enamel hardness and surface morphology when performed as described in this study