title: Influence of remaining coronal structure and of the marginal design on the fracture strength of roots restored with cast post and core.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the fracture strength of roots that were prosthetically restored with cast post and core with or without any remaining coronal structure and with different finish lines.
  
  
  METHODS
  Sixty bovine incisors were sectioned below the cementoenamel junction, endodontically treated and randomly divided into six experimental groups (n = 10) containing teeth with or without any remaining coronal structure and with a beveled shoulder, a chanfered or a shoulder finish line design. The cast post and core were luted with dual-cured resin cement. The metal crowns were cemented with zinc phosphate cement. The specimens were subjected to a tangential compressive load (135° angle) at a crosshead speed of 0.5 mm/min until failure, using a universal testing machine. The fracture strength data were analyzed using the ANOVA and LSMeans (least square means) tests (α = 0.05).
  
  
  RESULTS
  The data indicated that the teeth with 2 mm of remaining coronal structure showed the highest fracture strength values when compared with the teeth without any remaining structure (p < 0.05). As to the different finish line designs, the highest fracture strength values were obtained for the beveled shoulder, followed by the chanfered and then by the shoulder designs (p < 0.05).
  
  
  CONCLUSIONS
  It may be concluded that, to increase fracture strength, a beveled shoulder and 2 mm of remaining coronal structure are the ideal conditions.
authors.affiliation: Department of Restorative Dentistry, Passo Fundo Dental School, University of Passo Fundo, Passo Fundo, RS, Brazil.
authors.forename: Bruno
authors.initials: B
authors.lastname: Carlini-Júnior
authors.forename: Doglas
authors.initials: D
authors.lastname: Cecchin
authors.forename: Ana P
authors.initials: AP
authors.lastname: Farina
authors.forename: Gisele D S
authors.initials: GD
authors.lastname: Pereira
authors.forename: Lúcia T
authors.initials: LT
authors.lastname: Prieto
authors.forename: Luis A M S
authors.initials: LA
authors.lastname: Paulillo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D019245:Compressive Strength; D003735:Dental Casting Technique; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D003804:Dentin; D007180:Incisor; D016018:Least-Squares Analysis; D011176:Post and Core Technique; D011897:Random Allocation; D019228:Tooth Crown / Q000473:pathology*; D014082:Tooth Fractures / Q000517:prevention & control*; D019231:Tooth Preparation, Prosthodontic / Q000379:methods; D014092:Tooth Root / Q000293:injuries