title: [Influence of post-core on the strength of endodontically treated and crowned teeth].
abstract: OBJECTIVE
  To investigate the influence of post-core structure on the strength of endodontically treated and crowned teeth with or without a 2.0 mm dentine ferrule.
  
  
  METHODS
  A total of 60 recently extracted human maxillary central incisors were endodontically treated and randomly divided into five groups of 12. They were given following treatments: Group A, endodontically treated; Group B, endodontically treated and crowned (PFM); Group C, cast metal post-core with 2.0 mm dentine ferrule and crowned (PFM); Group D, cast metal post-core with no dentine ferrule and crowned (PFM); Group E, prefabricated post and composite core with 2.0 mm dentine ferrule and crowned (PFM). All specimens were stored at 100% humidity at room temperature for 30 days before testing. Each specimen was in a special jig on the MTS 810 universal material testing machine and subjected to a load at a 135-degree angle to the long axis until failure, with crosshead speed of 0.02 cm/minute. Analysis of variance followed by the Newman-Keuls pairwise multiple comparison tests was used to compare the results.
  
  
  RESULTS
  There was a statistically significant difference between different restorative methods. The cast metal post-core with 2.0 mm dentine ferrule and crowned teeth had the highest fracture strength (1793.59 +/- 387.93N), followed by endodontically treated intact teeth (1466.68 +/- 240.11N). No significant difference in the fracture strength was found among the other three groups (958.49 +/- 286.02N; 992.98 +/- 291.00N; 994.94 +/- 285.04 N). There was a statistically significant difference in the fracture resistance between crowned teeth with and without 2.0 mm dentine ferrule (P < 0.01).
  
  
  CONCLUSIONS
  Not all post-core structure could improve the strength of endodontically treated teeth. The dentine ferrule can effectively improve the fracture resistance of endodontically treated and crowned teeth.
authors.affiliation: Department of Dentistry, Beijing Hospital, Beijing 100730, China.
authors.forename: Zhiyue
authors.initials: Z
authors.lastname: Lu
authors.forename: Yuxing
authors.initials: Y
authors.lastname: Zhang
authors.forename: Weihong
authors.initials: W
authors.lastname: Zhang
authors.forename: Mengtao
authors.initials: M
authors.lastname: Wang
mesh_terms: D001696:Biomechanical Phenomena; D003442:Crowns; D006801:Humans; D013314:Stress, Mechanical; D019553:Tooth, Nonvital