title: Coronal resistance to fracture of endodontically treated teeth submitted to light-activated bleaching.
abstract: OBJECTIVE
  The aim of this study was to assess the fracture resistance of endodontically treated teeth submitted to bleaching with 38% hydrogen peroxide activated by light-emitting diode (LED)-laser system.
  
  
  METHODS
  Fifty maxillary incisors were endodontically treated, received a zinc phosphate barrier and were embedded in acrylic resin until cemento-enamel junction. The specimens were distributed into five groups (n=10) according to the number of bleaching sessions: GI, no treatment (control); GII, one session; GIII, two sessions; GIV, three sessions and GV, four sessions. The whitening gel was applied to the buccal surface of the tooth and inside the pulp chamber for three times in each session, followed by LED-laser activation. Specimens were submitted to the fracture resistance test (kN) and data were submitted to the Tukey-Kramer multiple comparisons test.
  
  
  RESULTS
  No significant difference (p>0.05) was found between GI (0.71+/-0.30) and GII (0.65+/-0.13), which presented the highest strength values to fracture. Groups III (0.35+/-0.17), IV (0.23+/-0.13) and V (0.38+/-0.15) showed lower resistance to fracture (p<0.01) when compared to GI and GII.
  
  
  CONCLUSIONS
  The fracture resistance of endodontically treated teeth decreased after two sessions of bleaching with 38% hydrogen peroxide activated by LED-laser system.
authors.affiliation: University of Ribeirão Preto, School of Dentistry, Av. Costabile Romano 2200, Ribeirão Preto 14096-900, SP, Brazil.
authors.forename: Priscila de Oliveira da Silva
authors.initials: Pde O
authors.lastname: Pobbe
authors.forename: Raqueli
authors.initials: R
authors.lastname: Viapiana
authors.forename: Aline Evangelista
authors.initials: AE
authors.lastname: Souza-Gabriel
authors.forename: Melissa Andréia
authors.initials: MA
authors.lastname: Marchesan
authors.forename: Manoel Damião
authors.initials: MD
authors.lastname: Sousa-Neto
authors.forename: Yara Teresinha Correa
authors.initials: YT
authors.lastname: Silva-Sousa
authors.forename: Ricardo Gariba
authors.initials: RG
authors.lastname: Silva
mesh_terms: D003799:Dental Stress Analysis; D006801:Humans; D006861:Hydrogen Peroxide / Q000009:adverse effects* / Q000528:radiation effects; D007180:Incisor; D007834:Lasers; D008027:Light; D008437:Maxilla; D016877:Oxidants / Q000009:adverse effects* / Q000528:radiation effects; D018709:Statistics, Nonparametric; D013997:Time Factors; D014073:Tooth Bleaching / Q000009:adverse effects* / Q000379:methods; D014082:Tooth Fractures / Q000517:prevention & control*; D019553:Tooth, Nonvital
chemical_list: D016877:Oxidants; D006861:Hydrogen Peroxide