title: Effect of protective coating on marginal integrity of nanohybrid composite during bleaching with carbamide peroxide: A microleakage study.
abstract: OBJECTIVE
  The aim of the study was to evaluate the microleakage on the marginal integrity of nanohybrid composite during bleaching with carbamide peroxide after applying a protective coating of G-Coat plus (GC, Japan).
  
  
  METHODS
  Class V cavities were prepared and restored with nanohybrid composite restoration in 60 freshly extracted noncarious premolars extracted for orthodontic reasons. Then they were divided into 3 groups. Group 1 - bleaching with carbamide peroxide without G coat plus (n = 20), Group 2 - bleaching with carbamide peroxide with G-Coat plus (n = 20), Group 3 - without bleaching procedure (n = 20) (control group). In Group 2, G coat plus was applied over the restorative surface and margins. Then all teeth in Groups 1 and 2 were taken and mounted in dental stone. Bleaching trays were custom fabricated over the cast with the help of a heated vacuum-forming machine. 10% carbamide peroxide (opalescence PF) was applied over the tooth, and the bleaching process was done for about 2 weeks. Then all samples underwent thermocycling and were then immersed in the 2% methylene blue solution for 24 h and observed under a stereomicroscope to evaluate the amount of dye penetration. Data were compared using Kruskal-Wallis test and Mann-Whitney test using SPSS Inc.; Chicago, IL, USA, Version 17.0.
  
  
  RESULTS
  Mann-Whitney test shows that the difference in microleakage between Group 1-Group 2 and Group 2-Group 3 is statistically significant (P < 0.05).
  
  
  CONCLUSIONS
  Significant reduction in microleakage was seen in Group 2 when compared to other groups.
authors.forename: A Ashok
authors.initials: AA
authors.lastname: Kumar
authors.affiliation: Department of Pedodontics and Preventive Dentistry, SRM Kattankulathur Dental College and Hospital, Chennai, Tamil Nadu, India.
authors.forename: V P
authors.initials: VP
authors.lastname: Hariharavel
authors.forename: Ashwin
authors.initials: A
authors.lastname: Narayanan
authors.forename: S
authors.initials: S
authors.lastname: Murali
mesh_terms: D001641:Bicuspid; D000077463:Carbamide Peroxide; D003188:Composite Resins / Q000737:chemistry*; D003738:Dental Cements / Q000737:chemistry; D003763:Dental Leakage; D003764:Dental Materials; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D010545:Peroxides / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry; D014073:Tooth Bleaching; D014508:Urea / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C554641:Adper single bond 2; C520091:CeramX; D003188:Composite Resins; D003738:Dental Cements; D003764:Dental Materials; C092621:Ivoclar Universal Cement; D010545:Peroxides; D019279:Resin Cements; D000077463:Carbamide Peroxide; D014508:Urea