title: Fracture toughness measurement of dental ceramics using the indentation fracture method with different formulas.
abstract: This study examined fracture toughness (KIC) measurements obtained using the indentation fracture (IF) method with a view to improving their reliability. The KIC values of five dental ceramics were measured using the IF method with five different formulas, and the single-edge precracked beam (SEPB) method was used as a control. The elastic moduli of the dental ceramics were evaluated by dynamic hardness test. Load conditions of the dental ceramics that produced a median/radial crack for the IF method formulas were investigated. Based on the resultant c/a and P/c1.5 values, the indentation load (P) required for median/radial crack occurrence varied greatly from 29.4 to 196 N depending on the ceramic used. Among the five formulas, none of the KIC values obtained by the IF method with Miyoshi's formula differed significantly (p > 0.05) from the values obtained using SEPB method. These results suggested that, after an appropriate indentation load is determined, reliable KIC values for small dental ceramic specimens can be easily obtained using the IF method if Miyoshi's formula is used in combination with the dynamic hardness test.
authors.affiliation: Department of Oral Biomaterials and Technology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Maehara
authors.forename: Akihiro
authors.initials: A
authors.lastname: Fujishima
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hotta
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyazaki
mesh_terms: D000465:Algorithms; D000537:Aluminum Oxide / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000379:methods / Q000706:statistics & numerical data; D004548:Elasticity; D006244:Hardness; D006801:Humans; D018020:Lithium Compounds / Q000737:chemistry; D008422:Materials Testing; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: C118557:Empress 2; D018020:Lithium Compounds; C465647:olympus castable ceramic; D003776:Dental Porcelain; C070870:In-Ceram; D000537:Aluminum Oxide