title: Fracture toughness of various core build-up materials.
abstract: OBJECTIVE
  The purpose of this investigation was to compare the fracture toughness of several core materials.
  
  
  METHODS
  Five core build-up materials were tested: (1) glass ionomer, (2) resin-modified glass ionomer, (3) titanium-reinforced composite, (4) composite resin with fluoride, and (5) amalgam. Fracture toughness determinations were made using 3-point flexure of beams with a central single-edge notch. The notch was standardized by the use of a special mold into which each of the materials was condensed. Ten beams of each material were tested on an Instron test machine (Instron Corp, Canton, MA) at a crosshead speed of 1.25 mm/min. The maximum loads were determined from which the fracture toughness values (KIC) were calculated. The data were analyzed statistically using analysis of variance and t tests.
  
  
  RESULTS
  The mean fracture toughness value in MN.m-3/2 for each of them is as follows: (1) glass ionomer, 0.717 +/- 0.071; (2) resin-modified glass ionomer, 0.747 +/- 0.061; (3) titanium-reinforced composite, 1.409 +/- 0.051; (4) composite resin with fluoride, 1.660 +/- 0.086; and (5) amalgam, 1.521 +/- 0.081. There was no significant difference in the KIC values for the glass ionomer-based materials, and both of these were significantly lower than amalgam, titanium-reinforced composite resin, and composite resin with fluoride (p < .001).
  
  
  CONCLUSIONS
  The titanium-reinforced composite resin, the composite resin with fluoride, and amalgam materials showed fracture toughness most likely to withstand the stresses generated during mastication.
authors.affiliation: Division of Restorative Dentistry, UCLA School of Dentistry, Los Angeles, CA, USA.
authors.forename: E D
authors.initials: ED
authors.lastname: Bonilla
authors.forename: G
authors.initials: G
authors.lastname: Mardirossian
authors.forename: A A
authors.initials: AA
authors.lastname: Caputo
mesh_terms: D000704:Analysis of Variance; D001732:Bite Force; D003188:Composite Resins / Q000737:chemistry; D003723:Dental Amalgam / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D005459:Fluorides / Q000737:chemistry; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D018583:Pliability; D011176:Post and Core Technique; D019279:Resin Cements / Q000737:chemistry; D013223:Statistics as Topic; D013314:Stress, Mechanical; D014025:Titanium / Q000737:chemistry
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D005899:Glass Ionomer Cements; D019279:Resin Cements; D003723:Dental Amalgam; D014025:Titanium; D005459:Fluorides