title: The fracture toughness of various core materials.
abstract: OBJECTIVE
  This study determined the fracture toughness of four core buildup materials.
  
  
  METHODS
  Single-edge notch, bar-shaped specimens conforming to the American Society for Testing Materials standard E-399 were fabricated for a high copper amalgam alloy, two composite resins, and a glass ionomer buildup material. The specimens were stored in air for 1 week and then tested in three-point bending mode with an Instron Universal Testing Machine (Instron Corporation, Canton, MA).
  
  
  RESULTS
  Fracture toughness values obtained were as follows: Fluorocore (composite resin; Caulk, Milford, DE), 1.54 MN.m-1.5; Ti-Core (composite resin and titanium; Essential Dental Systems, New York, NY), 1.34 MN.m-1.5; Valiant Ph.D. (amalgam; Caulk), 1.29 MN.m-1.5; and Coreshade Glass Ionomer Base Cement (Shofu Inc, Kyota, Japan), 0.55 MN.m-1.5.
  
  
  CONCLUSIONS
  Glass ionomer materials are probably unsuitable as core buildup materials because of their relatively low fracture toughness. Fluorocore, Ti-Core, and amalgam all had fracture toughness values significantly greater than the glass ionomer (P < .01).
authors.affiliation: Department of Restorative Sciences, Marquette University, School of Dentistry, Milwaukee, WI 53233, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Ziebert
authors.forename: V B
authors.initials: VB
authors.lastname: Dhuru
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D003300:Copper; D003723:Dental Amalgam / Q000737:chemistry*; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006244:Hardness; D008422:Materials Testing; D018583:Pliability; D011176:Post and Core Technique / Q000295:instrumentation*; D012015:Reference Standards; D013718:Tensile Strength; D014025:Titanium
chemical_list: D003188:Composite Resins; D005899:Glass Ionomer Cements; D003300:Copper; D003723:Dental Amalgam; D014025:Titanium