In this paper we present the results of an experiment with a commercial gel containing carbamide peroxide (CP) 15% (Opalescence 15% PF), aimed to assess the effects of this bleaching agent on the enamel surface of extracted human teeth, by using scanning electron microscopy (SEM). Opalescence 15% PF was applied on two quadrants of twelve extracted permanent, decay-free, human teeth, for 3 hours or 8 hours; for four teeth the application was performed once, while for eight teeth the treatment was repeated daily for 14 days (in order to simulate the usual clinical protocol of at-home bleaching). One quadrant of each tooth was used for control and the remaining quadrant was etched for 40 seconds with a gel containing 37% phosphoric acid. No differences concerning the micromorphology of tooth surface were observed by SEM, on the samples treated with Opalescence 15% PF once, for 3 or 8 hours, when compared to the control. Various, mainly minor changes occurred in samples treated with Opalescence 15% PF for 3 hours or 8 hours daily, for 14 days. On the other hand, the acid-etched samples had an irregular surface, which suggests important alterations of the prismatic structure of the enamel. These are the first studies of this type performed in Romania.