title: Fracture toughness of dental ceramics: comparison of bending and indentation method.
abstract: OBJECTIVE
  The aim of this study was to compare two fracture toughness methods, the bending method on notched specimens as reference and the indentation method as comparison. Potentialities and limitations of the indentation method were analyzed.
  
  
  METHODS
  Fracture toughness values were determined for seven dental ceramic materials on 'single-edge-v-notched beams' (bending method) as our standard method. Additionally indentation tests were done on the identical samples from the bending tests. The results were determined before and after annealing of the samples. With the reference fracture toughness results from the bending tests, the prefactor in the indentation test formula was individually adapted for each tested material.
  
  
  RESULTS
  The individual prefactors varied between 0.0122 and 0.0253 for the specimens before annealing and between 0.0150 and 0.0267 for the annealed specimens. Subsequently the differences between the K Ic-values calculated by the ISO draft (TC 206) direction and calculated by the modified formulae with the material specific prefactors were up to 48% for unannealed and up to 33% for annealed specimens, respectively.
  
  
  CONCLUSIONS
  The indentation method is not an adequate tool to exactly determine the fracture toughness of an unknown ceramic material. This method can only be used for a first rough K Ic estimation.
authors.affiliation: Department of Dental Prosthetics, Section of Dental Materials, University of Technology, Aachen, Germany. h.fischer@rwth-aachen.de
authors.forename: Horst
authors.initials: H
authors.lastname: Fischer
authors.forename: Rudolf
authors.initials: R
authors.lastname: Marx
mesh_terms: D000465:Algorithms; D000537:Aluminum Oxide / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry; D004548:Elasticity; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing / Q000379:methods; D018583:Pliability; D013314:Stress, Mechanical
chemical_list: D000538:Aluminum Silicates; C095718:Duceram; C075815:IPS-Empress ceramic; C110711:vita omega; D003776:Dental Porcelain; C074543:Cerec; C070870:In-Ceram; D017886:Durapatite; D000537:Aluminum Oxide