title: Indentation fracture toughness and dynamic elastic moduli for commercial feldspathic dental porcelain materials.
abstract: OBJECTIVE
  The purpose of this study was to evaluate and compare the indentation fracture toughness, true hardness and dynamic elastic moduli for 14 commercial dental porcelain materials.
  
  
  METHODS
  The specimens were fired according to manufacturer instructions. The density of the specimens (n=3) was measured by means of the water displacement technique. Dynamic Young's shear and bulk moduli and Poisson's ratio (n=3) were measured using a non-destructive ultrasonic technique using 10 MHz lithium niobate crystals. The true hardness (n=3) was measured using a Knoop indenter and the fracture toughness (n=3) was determined using a Vickers indenter and a Tukon hardness tester. Statistical analysis of the data was conducted using ANOVA and a Student-Newman-Keuls (SNK) rank order multiple comparative test.
  
  
  RESULTS
  The SNK rank test analysis for the mean dynamic Young's modulus and fracture toughness was able to separate 14 dental porcelain materials into seven and nine groups, respectively, at p=0.05. The elastic moduli, true hardness and indentation fracture toughness for opaque porcelains were significantly higher than incisal; and body materials at p=0.05.
  
  
  CONCLUSIONS
  The indentation fracture toughness and the ultrasonic test methods exhibit lower coefficient of variation compared to conventional methods and have considerable advantage for ceramic dental materials in that only small specimens are required to produce an acceptable number of data for statistical analysis.
authors.affiliation: Division of Biomaterials Science, School of Dentistry, The University of Western Ontario, N6A 5C1 London, Ont., Canada. arizkalla@eng.uwo.ca
authors.forename: Amin S
authors.initials: AS
authors.lastname: Rizkalla
authors.forename: Derek W
authors.initials: DW
authors.lastname: Jones
mesh_terms: D000538:Aluminum Silicates; D000704:Analysis of Variance; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D004548:Elasticity; D006244:Hardness; D008422:Materials Testing / Q000379:methods; D017680:Potassium Compounds; D018709:Statistics, Nonparametric; D014465:Ultrasonics
chemical_list: D000538:Aluminum Silicates; D017680:Potassium Compounds; D003776:Dental Porcelain; C016447:feldspar