title: In vitro fatigue resistance of glass ionomer cements used in post-and-core applications.
abstract: BACKGROUND
  New glass ionomer cements exhibit better mechanical properties than their older counterparts. However, there is concern about their use as a core material in post-and-core applications.
  
  
  OBJECTIVE
  This in vitro study evaluated the fatigue resistance of 2 new glass ionomer cements, Shofu Hi-Dense and Fuji IX GP, and compared their mechanical behavior as a core material under masticatory load with a silver-reinforced glass ionomer (ESPE Ketac-Silver) and a silver amalgam (Cavex Avaloy LC).
  
  
  METHODS
  A total of 100 commercial plastic teeth were divided into 4 groups of 25 specimens each. Titanium posts were placed in the prepared root canals, and cores were built up in amalgam, silver-reinforced glass ionomer cement, and the 2 new glass ionomer cements. The post-and-core specimens were prepared for full cast metal crowns, which were fabricated and cemented with glass ionomer cement. Twenty specimens from each group were placed in a mastication simulator and cyclically loaded with a 400 N force for 1.5 million cycles. The 5 remaining specimens were used as controls. The specimens were sectioned and observed macroscopically and microscopically to determine the number of defects (alterations) in each material. Observed defects were verified with the Kruskal-Wallis test, and the 4 core materials were ranked with the Tukey multiple comparisons test.
  
  
  RESULTS
  The mean rank sum values of the defects were as follows: Cavex Avaloy LC Amalgam (16.75), Fuji IX GP (38.50), Shofu Hi-Dense (39.53), and ESPE Ketac-Silver (67.22). The amalgam alloy was significantly different (P< .05) from the others.
  
  
  CONCLUSIONS
  Under the conditions of this study, the 2 new glass ionomer cements used as core materials showed a higher number of defects than amalgam. These results suggest that their fatigue resistance may be inadequate for post-and-core applications.
authors.affiliation: Department of Prosthodontics, University of Paris, and Structural Metallurgy Laboratory, Ecole Nationale Supérieure de Chimie, 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: D016722:Cermet Cements; D003723:Dental Amalgam; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements; D008422:Materials Testing; D011176:Post and Core Technique; D018709:Statistics, Nonparametric
chemical_list: D016722:Cermet Cements; D005899:Glass Ionomer Cements; C101939:Shofu High Dense; C110713:fuji IX; D003723:Dental Amalgam