title: Influence of the duration of treatment using a 10% carbamide peroxide bleaching gel on dentin surface microhardness: an in situ study.
abstract: This in situ study evaluated the influence of two home-use tooth bleaching regimes (1 hour/day and 7 hours/day) using 10% carbamide peroxide (Nite White Excel 2Z) on the surface microhardness of dentin over a 21-day period. Nine blocks of dentin derived from the teeth of subjects, each with at least two thirds molar in need of extraction, were obtained from the cervical region and submitted to surface-hardness analysis (Shimadsu HMV/2000), fixed to an intraoral palate device fabricated for each subject, and positioned (3 left side, 3 right side, 3 center) according to experimental group. During the bleaching period, casts bearing the whitening agent were applied to the blocks for 7, 1, and 0 hours, respectively (7 left side, 3 right side, 0 center). After the treatment period, the specimens were once again submitted to microhardness analysis, using the same equipment as before, and then analysis of variance and the Scheffé test were applied to the mean differences between the initial and final evaluations. The results demonstrated that the statistical difference between the 1-hour and 7-hour groups was not significant. However, the 7-hour group, when compared with the control group, demonstrated statistically significant differences with a reduction in microhardness. Despite the occurrence of mineral loss in the 1-hour and 7-hour groups, this difference was only 3.1% and 5.4%, respectively, which allows one to conclude that these values probably have no clinical significance.
authors.affiliation: Universidade Federal de Santa Catarina, Florianópolis, Brazil.
authors.forename: Gilberto Müller
authors.initials: GM
authors.lastname: Arcari
authors.forename: Luiz Narciso
authors.initials: LN
authors.lastname: Baratieri
authors.forename: Hamilton Pires
authors.initials: HP
authors.lastname: Maia
authors.forename: Sérgio Fernando Torres
authors.initials: SF
authors.lastname: De Freitas
mesh_terms: D000293:Adolescent; D000328:Adult; D000077463:Carbamide Peroxide; D003804:Dentin / Q000187:drug effects* / Q000473:pathology; D004338:Drug Combinations; D005260:Female; D006244:Hardness; D006801:Humans; D008297:Male; D016877:Oxidants / Q000008:administration & dosage / Q000627:therapeutic use*; D010545:Peroxides / Q000008:administration & dosage / Q000627:therapeutic use*; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods*; D014508:Urea / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000627:therapeutic use*
chemical_list: D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea