Micromorphology and surface roughness of sound and demineralized enamel and dentin bleached with a 10% carbamide peroxide bleaching agent.

PURPOSE

To evaluate the micromorphology and surface roughness of sound and demineralized enamel and dentin treated with a 10% carbamide peroxide bleaching agent in situ for 3 weeks.

METHODS

A 10% carbamide peroxide bleaching agent, Opalescence (OPA) was evaluated and a placebo agent (PLA) not containing carbamide peroxide, was used as a control group. Forty dental slabs [10 sound enamel slabs (SE), 10 demineralized enamel slabs (DE), 10 sound dentin slabs (SD) and 10 demineralized dentin slabs (DD)] were randomly fixed on the facial surface of the first maxillary molars and second maxillary premolars of 10 volunteers. Demineralized enamel and dentin fragments were obtained by a dynamic model using demineralizing and remineralizing solutions. The volunteers were divided into two groups that received the bleaching or the placebo agent in different sequences and periods in a double blind 2 x 2 cross-over study with a wash-out period of 2 weeks. Roughness was performed on the slab surfaces followed by scanning electron microscope (SEM) evaluations. The images were evaluated by three calibrated examiners in duplicate in two different periods at x1500 (SE and DE) and x2000 original magnification (SD and DD).

RESULTS

The Wilcoxon test showed significant differences in roughness for SE and DE treated with OPA or PLA, with rougher surfaces treated with OPA. No differences in roughness were observed for SD or DD treated with OPA or PLA. As the Kappa value for the inter-examiner agreement of SEM evaluations showed "moderate" reproducibility (0.41 < k< 0.60) in Period 1 and "substantial" (0.61 < k < 0.8) in Period 2, the latter was considered for the statistical analysis. The McNemar test showed no significant differences between SE, DE, SD or DD treated with OPA or PLA.