Fracture toughness (K(IC) of a hot-pressed core ceramic based on fractographic analysis of fractured ceramic FPDs.
OBJECTIVE
The objective of this study was to test the hypothesis that there is no significant difference between the fracture toughness (K(IC)) of an experimental hot-pressed core ceramic measured by fractographic analysis of failed ceramic prostheses and the values determined by other standard methods.


METHODS
Four groups were subjected to one of four test methods: group 1 = indentation strength technique (standard numerical calculation); group 2 = indentation strength technique (fractographic analysis); group 3 = flexure test of precracked specimens (fractographic analysis); and group 4 = fractographic analysis of failed three-unit fixed partial dentures (FPD). For groups 1 to 3, 20 ceramic bar specimens were subjected to three-point flexure at a cross-head speed of 0.5 mm/min until fracture occurred. For group 4, 10 failed FPDs were collected from a previous study. Stress values at failure were calculated from either a flexure stress equation (groups 1 to 3) or from finite element analyses (group 4). K(IC) values were calculated from an equation and fractographic measurement data.


RESULTS
Mean fracture toughness ranged from 3.1 MPa x m1/2 (SD 0.2) (group 1) to 3.4 MPa x m1/2 (SD 0.2) (group 4). The mean K(IC) value for group 1 was significantly different from that of group 4; however, no significant differences were found between groups 1, 2, and 3, or between groups 2, 3, and 4.


CONCLUSIONS
Fracture toughness for an experimental hot-pressed core ceramic measured by fractographic analysis in combination with finite element analysis was comparable with the values determined with other standard fractographic methods.
Oh
Won-Suck
WS
Department of Prosthodontics, College of Dentistry, University of Florida, Gainesville 32610-0435, USA. woh@dental.ufl.edu
Park
Ju-Mi
JM
Anusavice
Kenneth
K
D000704:Analysis of Variance; D002516:Ceramics / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003830:Denture, Partial, Fixed; D020342:Finite Element Analysis; D005898:Glass / Q000737:chemistry; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D013314:Stress, Mechanical; D013499:Surface Properties
D003764:Dental Materials