title: Er:YAG pre-treatment for bonding of orthodontic bracket: 1 year of in vitro treatment.
abstract: OBJECTIVE
  The aim of this study was to evaluate in vitro bond strength of metal brackets bonded with: total etch, total etch with erbium: yttrium aluminum garnet laser (Er:YAG) and self-etching adhesive systems, submitted to thermal-mechanical cycling, simulating 1 year of orthodontic treatment.
  
  
  METHODS
  For the study, 80 bovine incisors were randomly divided into 3 experimental groups (n=16 each): XT- acid etching + Transbond XT, XT/Er:YAG- Transbond XT associated with Er:YAG laser irradiation (λ=2.94 μm, 60 mJ, 10 Hz) and SEP- Transbond Plus Self Etching Primer. Samples were submitted to thermal-mechanical cycling, simulating 1 year of orthodontic treatment. Afterward, the shear bond strength test was performed in a universal test machine at a speed of 0.5mm/min. Samples were evaluated under a stereomicroscope and by scanning electron microscopy for analysis of enamel surface and adhesive remnant index. Data were analyzed using Kruskal-Wallis and Mann-Whitney (with Bonferroni correction) statistical tests.
  
  
  RESULTS
  Statistically significant difference was observed between the groups studied (p<0.05). Groups XT and SEP showed the highest bond strength values, without statistical difference between them, while group XT/Er:YAG showed reduction in bond strength values. Higher frequency of adhesive failures between enamel and adhesive system was verified for groups XT and XT/Er:YAG.
  
  
  CONCLUSIONS
  The conventional (XT) and self-etching (SEP) adhesive systems showed mean bond strength values, similar between them, whereas the previous application of Er:YAG laser promoted the lowest bond strength values.
authors.affiliation: Department of Dentistry, Ceuma University (UNICEUMA).
authors.forename: Rudys Rodolfo
authors.initials: RR
authors.lastname: de Jesus Tavarez
authors.affiliation: Dentistry Program, Ceuma University (UNICEUMA).
authors.forename: Gisele
authors.initials: G
authors.lastname: Lima Bezerra
authors.affiliation: Dentistry Program, Federal University of Maranhão, UFMA, São Luís, MA.
authors.forename: Karla Janilee
authors.initials: KJ
authors.lastname: de Souza Penha
authors.affiliation: Restorative Dentistry Department, ICT UNESP University, São Paulo.
authors.forename: Carlos Rocha Gomes
authors.initials: CR
authors.lastname: Torres
authors.affiliation: Dentistry Department I, Federal University of Maranhão,UFMA, São Luís, MA, Brazil.
authors.forename: Leily Macedo
authors.initials: LM
authors.lastname: Firoozmand
keywords: YAG laser; dentin-bonding agents; enamel; orthodontic bonding; orthodontic brackets; self-etching adhesive system; shear strength