title: Comparison of two fracture toughness testing methods using a glass-infiltrated and a zirconia dental ceramic.
abstract: OBJECTIVE
  The objective of this study was to compare the fracture toughness (KIc) obtained from the single edge V-notched beam (SEVNB) and the fractographic analysis (FTA) of a glass-infiltrated and a zirconia ceramic.
  
  
  METHODS
  For each material, ten bar-shaped specimens were prepared for the SEVNB method (3 mm × 4 mm × 25 mm) and the FTA method (2 mm × 4 mm × 25 mm). The starter V-notch was prepared as the fracture initiating flaw for the SEVNB method. A Vickers indentation load of 49 N was used to create a controlled surface flaw on each FTA specimen. All specimens were loaded to fracture using a universal testing machine at a crosshead speed of 0.5-1 mm/min. The independent-samples t-test was used for the statistical analysis of the KIc values at α=0.05.
  
  
  RESULTS
  The mean KIc of zirconia ceramic obtained from SEVNB method (5.4 ± 1.6 MPa·m(1/2)) was comparable to that obtained from FTA method (6.3 ± 1.6 MPa·m(1/2)). The mean KIc of glass-infiltrated ceramic obtained from SEVNB method (4.1 ± 0.6 MPa·m(1/2)) was significantly lower than that obtained from FTA method (5.1 ± 0.7 MPa·m(1/2)).
  
  
  CONCLUSIONS
  The mean KIc of the glass-infiltrated and zirconia ceramics obtained from the SEVNB method were lower than those obtained from FTA method even they were not significantly different for the zirconia material. The differences in the KIc values could be a result of the differences in the characteristics of fracture initiating flaws of these two methods.
authors.affiliation: Department of Prosthodontics, Faculty of Dentistry, Mahidol University, Bangkok, Thailand.
authors.forename: Premwara
authors.initials: P
authors.lastname: Triwatana
authors.forename: Phakphum
authors.initials: P
authors.lastname: Srinuan
authors.forename: Kallaya
authors.initials: K
authors.lastname: Suputtamongkol
keywords: Dental ceramics; Fracture toughness; Zirconia