title: [Effect of carbamide peroxide bleaching agents on micro-leakage of composite resin interface in vitro].
abstract: OBJECTIVE
  To evaluate the effect of carbamide peroxide (CP) bleaching agents at different concentrations and with different carriers on the micro-leakage of composite resin interface.
  
  
  METHODS
  Class V cavity (2 mm in diameter and 2 mm in depth) preparations were made at the enamelo-cemental junction on the buccal and lingual surfaces of 35 extracted human premolars. The cavities were filled with hybrid composite resin. The teeth were stored for 24 h in distilled water at 37 degrees celsius; before thermocyling for 500 times between 5 and 55 degrees celsius;. The teeth were then randomly assigned into 7 groups, and in groups 1-6, the bleaching gels containing 10% or 20% of CP were applied on the buccal and lingual surface of the teeth for two weeks (6-8 h/day, 37 degrees celsius;, 100% relative humidity) using Carbopol, PVP or Poloxamer as the thickening carriers, respectively. The seventh group served as the control without bleaching treatment. Nail polish was applied to the surface of the tooth, and all the teeth were immersed in ammoniacal silver nitrate solution followed by developing solution. The teeth were finally sectioned through the midline of the restoration and observed under stereomicroscope. SEM micrographs were also made to observe the interface.
  
  
  RESULTS
  With the same bleaching agent, the micro-leakage in the gingival wall was slightly greater than in the occlusive wall, but the difference was not significant. Only 20% CP with Poloxamer as the thickening agent significantly increased the leakage of dentine-resin composite interface, and 10% and 20% CP with Carbopol or PVP as the thickening agents and 10% CP with Poloxamer produced minimal effects on filling the micro-leakage.
  
  
  CONCLUSIONS
  Thickening carriers and the concentration of CP (20% or below) have no significant effect on micro-leakage of composite resin.
authors.affiliation: Department of Stomatology, General Hospital of the Armed Police Forces, Beijing 100039, China. wxl1018@yahoo.com.cn
authors.forename: Xiao-ling
authors.initials: XL
authors.lastname: Wang
authors.forename: Juan
authors.initials: J
authors.lastname: Xu
authors.forename: Xin-yi
authors.initials: XY
authors.lastname: Zhao
authors.forename: Hui-ming
authors.initials: HM
authors.lastname: He
mesh_terms: D001641:Bicuspid; D057886:Bleaching Agents / Q000737:chemistry*; D000077463:Carbamide Peroxide; D003188:Composite Resins / Q000737:chemistry*; D003731:Dental Caries / Q000628:therapy; D003763:Dental Leakage / Q000139:chemically induced*; D003793:Dental Restoration, Permanent / Q000379:methods; D006801:Humans; D010545:Peroxides / Q000737:chemistry*; D014073:Tooth Bleaching / Q000009:adverse effects*; D014508:Urea / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D057886:Bleaching Agents; D003188:Composite Resins; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea