title: Effects of two antioxidants on the microleakage of resin-based composite restorations after nonvital bleaching.
abstract: OBJECTIVE
  The aim of this study was to compare the neutralizing effect of antioxidant agents on the microleakage of dental restorations in nonvital teeth after bleaching with carbamide peroxide. Also assessed was the correlation of the microleakage data between an electrochemical and a staining technique.
  
  
  METHODS
  Following root canal therapy, 40 sound and similar human maxillary central incisors were randomly divided into four groups of 10 specimens each (n=10). The groups were subjected to one of four treatments: Group 1, bleaching with 10 percent carbamide peroxide for periods of eight hours per day for one week without an antioxidant agent; Group 2, bleaching with 10 percent carbamide peroxide plus 10 percent sodium ascorbate gel; Group 3, bleaching with 10 percent carbamide peroxide plus 10 percent sodium ascorbate gel combined with a surfactant; and Group 4, no bleaching treatment (control group). In all groups, the access cavities were restored using the Single Bond Plus Adhesive system and Z100 resin-based composite. After 1,000 thermal cycles, the teeth were dried and three layers of nail varnish were applied over the entire surface area to within 1.0 mm of the restoration. A PVC-covered copper wire, with 3.0 mm of exposed bare wire, was inserted apically 5.0 mm into the canal, which was obturated with gutta-percha and sealed with sticky wax and varnish at the apex. Leakage was continuously monitored for 40 days using a conductimetric method. The teeth were immersed in 0.5 percent basic fuchsine for 24 hours, followed by sectioning for microscopic examination at 16x magnification. The data were analyzed using ANOVA and the Newman-Keuls multiple comparison, Kruskal-Wallis, Mann-Whitney, and Spearman's rho tests (p<0.05).
  
  
  RESULTS
  Based on the electrochemical results, cavities subjected to 10 percent sodium ascorbate gel combined with a surfactant displayed the least amount of microleakage while teeth that were bleached but not treated with an antioxidant exhibited significantly greater microleakage (p=0.007). These findings also were corroborated by the results of the staining experiments that showed a strong correlation between the electrochemical and staining findings (p=0.006) for the groups.
  
  
  CONCLUSIONS
  After nonvital bleaching and the application of the antioxidant 10 percent sodium ascorbate, the addition of the surfactant 0.2 percent Tween 80 to the conventional antioxidant formulation significantly reduced microleakage.
  
  
  CONCLUSIONS
  The addition of a surfactant to the antioxidant formulation significantly reduced microleakage when it was applied after bleaching.
authors.affiliation: Department of Restorative Dentistry of the School of Dentistry, Dental Material Research Center, Mashhad University of Medical Sciences, Mashhad, Iran. dentist_57@yahoo.com
authors.forename: Horieh
authors.initials: H
authors.lastname: Moosavi
authors.forename: Mohammad Javad
authors.initials: MJ
authors.lastname: Moghaddas
authors.forename: Jamileh
authors.initials: J
authors.lastname: Ghoddusi
authors.forename: Omid
authors.initials: O
authors.lastname: Rajabi
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D001205:Ascorbic Acid / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D000077463:Carbamide Peroxide; D004396:Coloring Agents; D003188:Composite Resins / Q000737:chemistry*; D003763:Dental Leakage / Q000145:classification*; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000379:methods*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D055664:Electrochemical Techniques; D005782:Gels; D006801:Humans; D008422:Materials Testing; D010545:Peroxides / Q000737:chemistry; D011136:Polysorbates / Q000737:chemistry; D012394:Rosaniline Dyes; D012822:Silicon Dioxide / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods*; D058205:Tooth Bleaching Agents / Q000737:chemistry*; D019553:Tooth, Nonvital / Q000628:therapy; D014508:Urea / Q000031:analogs & derivatives / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D000975:Antioxidants; D004396:Coloring Agents; D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; D005782:Gels; D010545:Peroxides; D011136:Polysorbates; D012394:Rosaniline Dyes; C511238:Single Bond Plus; D013501:Surface-Active Agents; D058205:Tooth Bleaching Agents; C083568:Z100 composite resin; D000077463:Carbamide Peroxide; D017438:Bisphenol A-Glycidyl Methacrylate; C025485:basic fuchsin; D012822:Silicon Dioxide; D014508:Urea; D015040:Zirconium; D001205:Ascorbic Acid