title: Effect of root canal preparation, type of endodontic post and mechanical cycling on root fracture strength.
abstract: OBJECTIVE
  To evaluate the impact of the type of root canal preparation, intraradicular post and mechanical cycling on the fracture strength of roots.
  
  
  METHODS
  eighty human single rooted teeth were divided into 8 groups according to the instruments used for root canal preparation (manual or rotary instruments), the type of intraradicular post (fiber posts- FRC and cast post and core- CPC) and the use of mechanical cycling (MC) as follows: Manual and FRC; Manual, FRC and MC; Manual and CPC; Manual, CPC and MC; Rotary and FRC; Rotary, FRC and MC; Rotary and CPC; Rotary, CPC and MC. The filling was performed by lateral compactation. All root canals were prepared for a post with a 10 mm length, using the custom #2 bur of the glass fiber post system. For mechanical cycling, the protocol was applied as follows: an angle of incidence of 45°, 37°C, 88 N, 4 Hz, 2 million pulses. All groups were submitted to fracture strength test in a 45° device with 1 mm/ min cross-head speed until failure occurred.
  
  
  RESULTS
  The 3-way ANOVA showed that the root canal preparation strategy (p<0.03) and post type (p<0.0001) affected the fracture strength results, while mechanical cycling (p=0.29) did not.
  
  
  CONCLUSIONS
  The root canal preparation strategy only influenced the root fracture strength when restoring with a fiber post and mechanical cycling, so it does not seem to be an important factor in this scenario.
authors.affiliation: Prosthodontic Unit, São José dos Campos Dental School, Univ. Estadual Paulista, São José dos Campos, SP, Brazil.
authors.forename: Marília Pivetta
authors.initials: MP
authors.lastname: Rippe
authors.affiliation: Endodontic Unit, Faculty of Odontology, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors.forename: Manuela Favarin
authors.initials: MF
authors.lastname: Santini
authors.affiliation: Endodontic Unit, Faculty of Odontology, Federal University of Santa Maria, Santa Maria, RS, Brazil.
authors.forename: Carlos Alexandre Souza
authors.initials: CA
authors.lastname: Bier
authors.affiliation: Prosthodontic Unit, Department of Biomedical Sciences, Oral Rehabilitation Unit, University of Bologna, Bologna, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Baldissara
authors.affiliation: Prosthodontic Unit, Department of Restorative Dentistry, Faculty of Odontology, Federal University of Santa Maria, Santa Maria, RS, Brazil.
authors.forename: Luiz Felipe
authors.initials: LF
authors.lastname: Valandro
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry; D003762:Dental Instruments; D003799:Dental Stress Analysis; D003804:Dentin / Q000033:anatomy & histology; D006801:Humans; D008422:Materials Testing; D011176:Post and Core Technique / Q000295:instrumentation*; D015203:Reproducibility of Results; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods*; D013314:Stress, Mechanical; D013499:Surface Properties; D014082:Tooth Fractures / Q000209:etiology* / Q000503:physiopathology; D014092:Tooth Root / Q000033:anatomy & histology / Q000293:injuries*
chemical_list: D003188:Composite Resins