title: Effect of CO2, Nd:YAG and Er:YAG Lasers on Microtensile Bond Strength of Composite to Bleached-Enamel.
abstract: BACKGROUND
  Tooth restoration immediately after bleaching is challenging due to the potential problems in achieving adequate bond strength.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the effect of surface treatment with ER:YAG, ND:YAG, CO2 lasers and 10% sodium ascorbate solution on immediate microtensile bond strength of composite resin to recently bleached enamel.
  
  
  METHODS
  Ninety sound molar teeth were randomly divided into three main groups (n:30) : NB (without bleaching), HB (bleached with 38% carbamide peroxide) and OB (bleached with Heydent bleaching gel assisted by diode laser). Each group was divided into five subgroups (n:6) : Si (without surface treatment), Er (Er:YAG laser), CO2 (CO2 laser), Nd (Nd:YAG laser) and As (Immersion in 10% sodium ascorbate solution). The bonding system was then applied and composite build-ups were constructed. The teeth were sectioned by low speed saw to obtain enamel- resin sticks and submitted to microtensile bond testing. Statistical analyses were done using two- way ANOVA, Tukey and Tamhane tests.
  
  
  RESULTS
  µTBS of bleached teeth irradiated with ND:YAG laser was not significantly different from NB-Nd group. Microtensile bond strength of OB-Er group was higher than NB-Er and HB-Er groups. The mean µTBS of HB-CO2 group was higher than NB-CO2 group; the average µTBS of HB-As and OB-As groups was also higher than NB-As group.
  
  
  CONCLUSIONS
  Use of Nd:YAG, CO2 lasers and 10% sodium ascorbate solution could improve the bond strength in home-bleached specimens. Application of ND:YAG laser on nonbleached specimens and Er:YAG laser on office-bleached specimens led to the highest µTBS in comparison to other surface treatments in each main group.
authors.affiliation: Department of Operative Dentistry, Shahed University, Tehran, Iran.
authors.forename: Mahshid Mohammadi
authors.initials: MM
authors.lastname: Basir
authors.affiliation: Department of Operative Dentistry, Shahed University, Tehran, Iran.
authors.forename: Mohammad Bagher
authors.initials: MB
authors.lastname: Rezvani
authors.affiliation: Laser Research Center of Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Nasim
authors.initials: N
authors.lastname: Chiniforush
authors.affiliation: Department of Operative Dentistry, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Zohreh
authors.initials: Z
authors.lastname: Moradi
keywords: Bleaching; CO2 laser; Er:YAG laser; Nd:YAG laser; microtensile bond strength; sodium ascorbate