title: The efficacy of three different in-office bleaching systems and their effect on enamel microhardness.
abstract: This in vitro study evaluated and compared the efficacy of three in-office bleaching systems and investigated their effect on enamel microhardness. Three groups of 12 teeth (third molars) each were bleached as follows: Group A: Opalescence Xtra Boost (38% HP), Group B: Easywhite Ready (30% HP) with plasma unit and Group C: Zoom2 system (25% HP with the Zoom2 unit). The teeth were stained with tea for 24 hours, followed by the appropriate bleaching procedure. Each bleaching cycle was conducted for 15 minutes. The bleaching procedure was repeated until a shade change of six tabs (VITA shade guide) was obtained. The shade of the teeth was evaluated before, immediately after bleaching and one month later, both visually and digitally. Additionally, the "change of shade tabs per minute" was calculated. For the digital evaluation, the photos were taken under the same circumstances and the L*a*b* values were calculated using Photoshop. Five additional enamel samples for each group were prepared, and Knoop microhardness was evaluated before and after 15 minutes of bleaching. According to the visual shade evaluation, the treatment cycles required to reach the defined level of bleaching were: 1.58 for Group A (23.7 minutes), 1.02 for Group B (16.2 minutes) and 1.25 for Group C (18.7 minutes). Immediately after bleaching, a significant difference was found between Groups A and B (p = 0.0094). However, one month after the bleaching procedure, no significant difference could be observed among the three groups. According to the digital evaluation, no significant differences were found among the three bleaching systems for each of the L*a*b* values and the three times tested (p > 0.05). No significant difference (p = 0.055) was noticed among the three groups regarding microhardness after bleaching.
authors.affiliation: University Medical Center Freiburg, Dental School and Hospital, Department of Operative Dentistry and Periodontology, Freiburg, Germany. olga.polydorou@uniklinik-freiburg.de
authors.forename: Olga
authors.initials: O
authors.lastname: Polydorou
authors.forename: Elmar
authors.initials: E
authors.lastname: Hellwig
authors.forename: Petra
authors.initials: P
authors.lastname: Hahn
mesh_terms: D000077463:Carbamide Peroxide; D003116:Color; D003118:Color Perception; D003124:Colorimetry; D003743:Dental Enamel / Q000187:drug effects*; D003770:Dental Offices; D004338:Drug Combinations; D005500:Follow-Up Studies; D006244:Hardness; D006801:Humans; D006861:Hydrogen Peroxide / Q000627:therapeutic use; D008422:Materials Testing; D055095:Optics and Photonics; D016877:Oxidants / Q000627:therapeutic use*; D010545:Peroxides / Q000627:therapeutic use; D013662:Tea; D013997:Time Factors; D014070:Tooth / Q000473:pathology; D014073:Tooth Bleaching / Q000379:methods*; D014075:Tooth Discoloration / Q000188:drug therapy; D014508:Urea / Q000031:analogs & derivatives / Q000627:therapeutic use
chemical_list: D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D013662:Tea; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide