The effect of six bleaching products on enamel whitening and microhardness

Abstract

The aim of this study was to test the effect of three professional bleaching systems and three over the counter bleaching agents (OTC) on enamel microhardness. The crowns of thirty-five human premolars were sectioned mesiodistaly and the obtained dental fragments were embedded in self-curing polyesterene resin in a ring mold. The specimens were then randomly divided into seven groups as per treatment modality (n=10): Opalescence Xtra, (35% hydrogen peroxide), Nite White (16% carbamide peroxide), Bleach 10 (10% carbamide peroxide), two non peroxide OTC bleaching systems (Rapid White gel, Rapid white 2 Steps Brush On), Natural white gel (hydrogen peroxide concentration is not indicated), and artificial saliva to serve as control. Before performing the bleaching procedure, the shade of all specimens was recorded using Vita shade guide. Vickers microhardness values for enamel surfaces were also recorded prior to treatment. The bleaching procedures were then conducted on enamel surfaces according to manufacturers’ instructions. The office bleaching agents was conducted once weekly for two weeks and the other home bleaching procedures were conducted daily for two weeks. Following each bleaching session, the specimens were kept in artificial saliva. Control specimens were kept in artificial saliva during the time of the study at 37 oC. After two weeks, the shade of all specimens and enamel microhardness were evaluated. Results indicated that specimens submitted to 35% hydrogen peroxide, 16% and 10% carbamide peroxide showed significant reduction in microhardness. 35% 3 hydrogen peroxide also produced the most significant whitening effect followed by 16% and 10% carbamide peroxide, where no significant difference was found between the last two products in microhardness or color. Enamel surfaces treated with OTC bleaching products did not show any significant color improvement also; no significant changes in microhardness values from baseline were recorded.King Saud Universit