title: Resistance to fracture of crowned endodontically treated premolars restored with ceramic and metal post systems.
abstract: OBJECTIVE
  The objective of this study was to assess the resistance to fracture of crowned endodontically treated premolars with varying ceramic and metal post systems under simulated occlusal load.
  
  
  METHODS
  The study consisted of 60 extracted intact premolars with similar root diameter and length. Teeth were divided equally into 4 groups (n = 15) and prepared for posts and cast crowns as follows: group 1 = preformed metal post, composite core, and cast crown; group 2 = cast post and core and cast crown; group 3 = zirconia post, composite core, and cast crown; and group 4 = zirconia post and heat-pressed ceramic core and cast crown. All prepared teeth had 2 mm of sound dentin on which the cast crowns were cemented. A continuous load (kg) was applied by an Instron testing machine to the buccal cusp at a 30-degree angle to the long axis of each tooth at a crosshead speed of 2 mm/min until failure. One-way analysis of variance with Scheffe test was used to statistically compare the differences between groups.
  
  
  RESULTS
  Mean failure loads (in newtons) for the 4 test groups were as follows: 1,103.3 (group 1), 1,234.5 (group 2), 826.6 (group 3), and 870.6 (group 4). No significant difference in failure load values was found among all tested groups (F[3,59] = 2.05; P >.05). The primary mode of failure (85%) in all groups was an oblique radicular fracture, either apical to the post or at the post level. Horizontal fracture (15% to 20%) of the root and post was found in groups 3 and 4.
  
  
  CONCLUSIONS
  Within the limitations of this study, varying ceramic and metal post systems did not affect the failure resistance of teeth restored with full-coverage cast metal crowns, under simulated occlusal load.
authors.affiliation: Department of Prosthodontics, The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel. nissandr@post.tau.ac.il <nissandr@post.tau.ac.il>
authors.forename: Joseph
authors.initials: J
authors.lastname: Nissan
authors.forename: Alex
authors.initials: A
authors.lastname: Parson
authors.forename: Eitan
authors.initials: E
authors.lastname: Barnea
authors.forename: Arie
authors.initials: A
authors.lastname: Shifman
authors.forename: David
authors.initials: D
authors.lastname: Assif
mesh_terms: D001641:Bicuspid / Q000737:chemistry*; D003442:Crowns; D003764:Dental Materials / Q000737:chemistry; D006801:Humans; D011176:Post and Core Technique; D014082:Tooth Fractures; D019553:Tooth, Nonvital; D015040:Zirconium / Q000737:chemistry
chemical_list: D003764:Dental Materials; D015040:Zirconium; C028541:zirconium oxide