title: Bleaching effect of ozone on pigmented teeth.
abstract: BACKGROUND
  There have been numerous researches on ozone application in dentistry; yet the data regarding its whitening effect is very limited. The present study compares the bleaching effect of ozone with office bleaching.
  
  
  METHODS
  In this experimental study, 15 maxillary premolar teeth were selected and sectioned mesio-distally and bucco-lingually. The sections were then placed in tea for 1 week according to the Sulieman method and were divided into three groups each comprised of 15 sections. The samples were bleached as followed; Group I: Bleached with 35% hydrogen peroxide in three intervals of 8 min each, Group II: Underwent ozone treatment using Ozotop unite for 4 min and Group III: Bleached with a combination of both methods. The color indices of the samples, i.e., (a) green-red pigment, (b) blue-yellow pigment, (L) brightness, (ΔE) overall color change, were evaluated pre- and post-bleaching utilizing a digital camera, Photoshop software and CIE lab index. The color changes of specimens then were calculated and analyzed through randomized analysis of variance and Tukey tests. P < 0.001 was considered to be significant.
  
  
  RESULTS
  The color change (ΔE) in Group II was significantly lower than those in the two other groups (P < 0.001). There was no significant difference between the color change of Groups I and III (P = 0.639). In addition, the results of L, a and b brought forth a similar pattern to the findings obtained from ΔE.
  
  
  CONCLUSIONS
  The hydrogen peroxide gel has a more powerful whitening effect than ozone; in addition, ozone has no synergistic effect when is used simultaneously with hydrogen peroxide.
authors.affiliation: Department of Restorative Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Vagharedin Akhavan
authors.initials: VA
authors.lastname: Zanjani
authors.affiliation: Department of Restorative Dentistry, Dental Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Amir
authors.initials: A
authors.lastname: Ghasemi
authors.affiliation: Department of Restorative Dentistry, Preventive Dentistry Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Torabzadeh
authors.affiliation: Private Practice, Tehran, Iran.
authors.forename: Mahbobeh
authors.initials: M
authors.lastname: Jamali
authors.affiliation: Iranian Center for Endodontic Research, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Sara
authors.initials: S
authors.lastname: Razmavar
authors.affiliation: Department of Biostatistics, School of Paramedical Sciences, Dental Research Center, Research Institute of Dental Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Alireza Akbarzadeh
authors.initials: AA
authors.lastname: Baghban
keywords: Hydrogen peroxide; ozone; tooth bleaching