title: Fatigue testing and microscopic evaluation of post and core restorations under artificial crowns.
abstract: BACKGROUND
  Coronoradicular reconstruction techniques of pulpless teeth include prefabricated post systems that retain a core material such as silver amalgam, composite, glass ionomer, or modified glass ionomer cement. Mechanical properties of these materials are critical to sustain masticatory forces.
  
  
  OBJECTIVE
  This in vitro study compared the mechanical resistance of 3 core materials (silver amalgam, composite, and silver-reinforced glass ionomer) under masticatory conditions.
  
  
  METHODS
  Industrially fabricated teeth were used and a total of 75 specimens were divided into 3 groups of 25 specimens. Titanium canal posts were placed, followed by core buildups in amalgam, composite, or glass ionomer. Teeth were prepared for full cast crowns and the crowns were fabricated and cemented with glass ionomer cement. Twenty specimens from each group were placed in a mastication simulator cyclically loading the teeth with a 400 N force for 1.5 million cycles. The 5 remaining specimens were used as controls. Teeth were sectioned and observed macroscopically and microscopically to determine the rate of defects for each material. Observed defects were verified with the Kruskal-Wallis test. The 3 core materials were ranked with the Tukey multiple comparison test.
  
  
  RESULTS
  Significant differences of mechanical behavior were found for the 3 materials. At P <.01, silver amalgam was significantly superior to composite and glass ionomer. Composite was significantly superior to glass ionomer.
  
  
  CONCLUSIONS
  Cores fabricated with amalgam had the lowest rate of defects when tested under artificial crowns. Glass ionomer, when used as a core material under artificial crowns, showed the highest rate of defects after an instantaneous load of 400 N for a 1,500,000 repetition cycle.
authors.affiliation: School of Dentistry, University of Paris VII, Paris, France. philippe.gateau2@wanadoo.fr
authors.forename: P
authors.initials: P
authors.lastname: Gateau
authors.forename: M
authors.initials: M
authors.lastname: Sabek
authors.forename: B
authors.initials: B
authors.lastname: Dailey
mesh_terms: D001696:Biomechanical Phenomena; D016722:Cermet Cements / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003442:Crowns; D003723:Dental Amalgam / Q000737:chemistry; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements / Q000737:chemistry; D008409:Mastication; D008422:Materials Testing; D011176:Post and Core Technique; D018709:Statistics, Nonparametric
chemical_list: D016722:Cermet Cements; D003188:Composite Resins; D005899:Glass Ionomer Cements; D003723:Dental Amalgam