title: Fracture resistance of teeth submitted to several internal bleaching protocols.
abstract: OBJECTIVE
  The aim of this study was to evaluate the fracture resistance of teeth submitted to several internal bleaching protocols using 35% hydrogen peroxide (35HP), 37% carbamide peroxide (37CP), 15% hydrogen peroxide with titanium dioxide nanoparticles (15HPTiO2) photoactivated by LED-laser or sodium perborate (SP).
  
  
  METHODS
  After endodontic treatment, fifty bovine extracted teeth were divided into five groups (n = 10): G1-unbleached; G2-35HP; G3-37CP; G4-15HPTiO2 photoactivated by LED-laser and G5-SP. In the G2 and G4, the bleaching protocol was applied in 4 sessions, with 7 days intervals between each session. In the G3 and G5, the materials were kept in the pulp teeth for 21 days, but replaced every 7 days. After 21 days, the teeth were subjected to compressive load at a cross head speed of 0.5 mm/min, applied at 135° to the long axis of the root using an eletromechanical testing machine, until teeth fracture. The data were submitted to ANOVA and Tukey tests (α = 5%).
  
  
  RESULTS
  The 35HP, 37CP, 15HPTiO2 and SP showed similar fracture resistance teeth reduction (p > 0.05). All bleaching treatments reduced the fracture resistance compared to unbleached teeth (p < 0.05).
  
  
  CONCLUSIONS
  All bleaching protocols reduced the fracture resistance of endodontically-treated teeth, but there were no differences between each other.
  
  
  CONCLUSIONS
  There are several internal bleaching protocols using hydrogen peroxide in different concentrations and activation methods. This study evaluated its effects on fracture resistance in endodontically-treated teeth.
authors.affiliation: Associate Professor, Department of Restorative Dentistry, Araraquara Dental School, UNESP-Univ Estadual Paulista, Araraquara, Säo Paulo, Brazil.
authors.forename: Renato de Toledo
authors.initials: Rde T
authors.lastname: Leonardo
authors.affiliation: Assistant Professor, Department of Restorative Dentistry, Araraquara Dental School, UNESP-Univ Estadual Paulista, Araraquara, Säo Paulo, Brazil.
authors.forename: Milton Carlos
authors.initials: MC
authors.lastname: Kuga
authors.affiliation: Postgraduate Student, Department of Restorative Dentistry, Araraquara Dental School, UNESP-Univ Estadual Paulista, Araraquara, Säo Paulo, Brazil.
authors.forename: Flávia Angélica
authors.initials: FA
authors.lastname: Guiotti
authors.affiliation: Postgraduate Student, Department of Restorative Dentistry, Araraquara Dental School, UNESP-Univ Estadual Paulista, Araraquara, Säo Paulo, Brazil.
authors.forename: Carolina
authors.initials: C
authors.lastname: Andolfatto
authors.affiliation: Assistant Professor, Department of Dentistry, Dental School, UFRN - Federal University, Rio Grande do Norte, Natal, Rio Grande do Norte Brazil.
authors.forename: Norberto Batista de
authors.initials: NB
authors.lastname: Faria-Júnior
authors.affiliation: Associate Professor, Department of Restorative Dentistry, Araraquara Dental School, UNESP-Univ Estadual Paulista, Araraquara, Säo Paulo, Brazil.
authors.forename: Edson Alves de
authors.initials: EA
authors.lastname: Campos
authors.affiliation: Postgraduate Student, Assistant Professor, Department of Restorative Dentistry, Araraquara Dental School, UNESP-Univ Estadual Paulista, Araraquara, Säo Paulo, Brazil.
authors.forename: Kátia Cristina
authors.initials: KC
authors.lastname: Keine
authors.affiliation: Assistant Professor, Department of Restorative Dentistry, Araraquara Dental School, UNESP-Univ Estadual Paulista, Araraquara, Säo Paulo, Brazil.
authors.forename: Andrea Abi Rached
authors.initials: AA
authors.lastname: Dantas
mesh_terms: D000818:Animals; D001881:Borates / Q000627:therapeutic use; D000077463:Carbamide Peroxide; D002417:Cattle; D003786:Dental Pulp Cavity / Q000187:drug effects*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006861:Hydrogen Peroxide / Q000627:therapeutic use; D028022:Low-Level Light Therapy; D008422:Materials Testing; D053758:Nanoparticles; D010545:Peroxides / Q000627:therapeutic use; D017319:Photosensitizing Agents / Q000627:therapeutic use; D011897:Random Allocation; D012390:Root Canal Therapy / Q000379:methods; D013314:Stress, Mechanical; D013997:Time Factors; D014025:Titanium / Q000627:therapeutic use; D014073:Tooth Bleaching / Q000379:methods*; D058205:Tooth Bleaching Agents / Q000627:therapeutic use*; D014082:Tooth Fractures / Q000503:physiopathology*; D014508:Urea / Q000031:analogs & derivatives / Q000627:therapeutic use
chemical_list: D001881:Borates; D010545:Peroxides; D017319:Photosensitizing Agents; D058205:Tooth Bleaching Agents; C009495:titanium dioxide; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide; D014025:Titanium; C027707:sodium perborate