title: Effect of Epigallocatechin Gallate on shear bond strength of composite resin to bleached enamel: an in vitro study.
abstract: OBJECTIVE
  The aim of this study was to determine the effect of epigallocatechin gallate (EGCG) on the shear bond strength of composite resin to bleached enamel.
  
  
  METHODS
  Ninety enamel surfaces of maxillary incisors were randomly divided into 9 groups as follows: G1: control (no bleaching); G2: bleaching; G3: bleaching and storage for seven days; G4 - 6: bleaching and application of 600, 800 and 1,000 µmol of EGCG-containing solution for 10 minutes, respectively; G7 - 9: bleaching and application of 600, 800 and 1,000 µmol of EGCG-containing solution for 20 minutes, respectively. The specimens were bleached with 30% hydrogen peroxide gel and a composite resin cylinder was bonded on each specimen using a bonding agent. Shear bond strength of the samples were measured in MPa. Data was analyzed using the two-way ANOVA and Tukey HSD tests (α = 0.05).
  
  
  RESULTS
  The maximum and minimum mean shear bond strength values were observed in G1 and G2, respectively. Time and concentration of EGCG showed no significant effects on bond strength of the groups (p > 0.05). Multiple comparison of groups did not reveal any significant differences between the groups except for G2 and all the other groups (p < 0.05).
  
  
  CONCLUSIONS
  There is a significant decrease in bond strength of composite resin to enamel immediately after bleaching. A delay of one week before bonding and the use of EGCG increased bond strength of composite resin to bleached enamel.
authors.affiliation: Dental Research Center, Department of Operative Dentistry, Dental School, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Khamverdi
authors.forename: Loghman
authors.initials: L
authors.lastname: Rezaei-Soufi
authors.forename: Shahin
authors.initials: S
authors.lastname: Kasraei
authors.forename: Negin
authors.initials: N
authors.lastname: Ronasi
authors.forename: Shiva
authors.initials: S
authors.lastname: Rostami
keywords: Antioxidant; Epigallocatechin gallate; Green tea; Shear bond strength; Tooth bleaching