title: Effective application duration of sodium ascorbate antioxidant in reducing microleakage of bonded composite restoration in intracoronally-bleached teeth.
abstract: OBJECTIVE
  The aim of this study was to determine an appropriate application duration of sodium ascorbate (SA) antioxidant gel in reducing microleakage of bonded composite restoration in intracoronally-bleached teeth.
  
  
  METHODS
  Eighty endodontically-treated human incisors were randomly divided into eight groups: control, no bleaching; IB and DB, immediate and delayed bonding after bleaching, respectively; S10m, S60m, S24h, S3d and S7d, bleaching + SA gel for 10 min, 60 min, 24 hr, 3 day and 7 day, respectively. For bleaching, a mixture of 30% hydrogen peroxide and sodium perborate was applied for 7 day. All access cavities were restored using One-Step adhesive (Bisco Inc.) and then Aelite LS Packable composite (Bisco Inc.). The bonded specimens were subjected to 500 thermal cycles, immersed in 1% methylene blue for 8 hr, and longitudinally sectioned. Microleakage was assessed with a 0 - 4 scoring system and analyzed using nonparametric statistical methods (α = 0.05).
  
  
  RESULTS
  Group IB showed a significantly higher microleakge than the control group (p = 0.006) and group DB a statistically similar score to the control group (p > 0.999). Although groups S10m, S60m, and S24h exhibited significantly higher scores than group DB (p < 0.05), the microleakage in groups S3d and S7d was statistically similar to that in group DB (p = 0.771, p > 0.999).
  
  
  CONCLUSIONS
  Application of SA gel for 3 day after nonvital bleaching was effective in reducing microleakage of composite restoration in intracoronally-bleached teeth.
authors.affiliation: Department of Conservative Dentistry, Kyungpook National University School of Dentistry, Daegu, Korea.
authors.forename: Jae-Young
authors.initials: JY
authors.lastname: Park
authors.forename: Tae-Yub
authors.initials: TY
authors.lastname: Kwon
authors.forename: Young-Kyung
authors.initials: YK
authors.lastname: Kim
keywords: Application duration; Composite restoration; Intracoronal bleaching; Microleakage; Sodium ascorbate