title: Bleaching effects on shear bond strengths of orthodontic brackets.
abstract: OBJECTIVE
  The purpose of this research was to investigate the influence of 35% hydrogen peroxide on orthodontic bracket adhesion at zero hour, 24 hours, 7, 21 and 56 days after dental bleaching.
  
  
  METHODS
  Ninety bovine incisors were prepared for adhesion test and adhesive remnant index (ARI) determination. The 35% hydrogen peroxide was used as a bleaching agent and the Transbond XT as a bonding agent.
  
  
  RESULTS
  Statiscally significant differences were observed between all the groups (p<0.001) and were observed in the comparison of zero hour and control group (p<0.001) and in the comparison of zero hour and 24 hours (p<0.001). ARI scores (0, 1, 2 e 3) also showed statiscally differences between all the groups (p=0.011) and at the comparison of all the test groups with the control: zero hour (p=0.001), 24 hours (p=0.009), 7 days (p=0.018), 21 days (p<0.001) e 56 days (p=0.004).
  
  
  CONCLUSIONS
  The shear bond strength values became significantly lower when the bracket was bonded immediately after bleaching and quickly returned to control level in 24 hours. In seven days, there was a slight increase that was not significant and recovered to normal values in the next weeks. Different patterns of fractures were observed in bleached enamel when ARI scores were analyzed. The control group showed a high frequency of 3 score and none of zero score, the opposite behavior was observed in the test groups.
authors.affiliation: Department of Orthodontics, Faculty of Dentistry, University of Rio de Janeiro State, Brazil. martins-mm@hotmail.com
authors.forename: Mariana M
authors.initials: MM
authors.lastname: Martins
authors.forename: Marco A
authors.initials: MA
authors.lastname: de Oliveira Almeida
authors.forename: Carlos N
authors.initials: CN
authors.lastname: Elias
authors.forename: Alvaro
authors.initials: A
authors.lastname: de Moraes Mendes
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000268:Adhesiveness; D000818:Animals; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D002417:Cattle; D001840:Dental Bonding / Q000379:methods*; D003743:Dental Enamel / Q000033:anatomy & histology; D003777:Dental Prophylaxis / Q000379:methods; D003799:Dental Stress Analysis / Q000295:instrumentation; D006861:Hydrogen Peroxide / Q000737:chemistry; D008422:Materials Testing; D016910:Orthodontic Brackets; D010756:Phosphoric Acids / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry*; D012464:Saliva, Artificial / Q000737:chemistry; D033081:Shear Strength; D017655:Silicon Compounds / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods*; D058205:Tooth Bleaching Agents / Q000737:chemistry*
chemical_list: D017554:Carbon Compounds, Inorganic; D010756:Phosphoric Acids; D019279:Resin Cements; D012464:Saliva, Artificial; D017655:Silicon Compounds; D058205:Tooth Bleaching Agents; C477790:Transbond XT; D006861:Hydrogen Peroxide; C030242:phosphoric acid; C022088:silicon carbide