title: Determination of the slow crack growth susceptibility coefficient of dental ceramics using different methods.
abstract: This study compared three methods for the determination of the slow crack growth susceptibility coefficient (n) of two veneering ceramics (VM7 and d.Sign), two glass-ceramics (Empress and Empress 2) and a glass-infiltrated alumina composite (In-Ceram Alumina). Discs (n = 10) were prepared according to manufacturers' recommendations and polished. The constant stress-rate test was performed at five constant stress rates to calculate n(d) . For the indentation fracture test to determine n(IF) , Vickers indentations were performed and the crack lengths were measured under an optical microscope. For the constant stress test (performed only for d.Sign for the determination of n(s) ) four constant stresses were applied and held constant until the specimens' fracture and the time to failure was recorded. All tests were performed in artificial saliva at 37°C. The n(d) values were 17.2 for Empress 2, followed by d.Sign (20.5), VM7 (26.5), Empress (30.2), and In-Ceram Alumina (31.1). In-Ceram Alumina and Empress 2 showed the highest n(IF) values, 66.0 and 40.2, respectively. The n(IF) values determined for Empress (25.2), d.Sign (25.6), and VM7 (20.1) were similar. The n(s) value determined for d.Sign was 31.4. It can be concluded that the n values determined for the dental ceramics evaluated were significantly influenced by the test method used.
authors.affiliation: Department of Biomaterials and Oral Biochemistry, School of Dentistry, University of São Paulo, São Paulo, Brazil.
authors.forename: Carla Castiglia
authors.initials: CC
authors.lastname: Gonzaga
authors.forename: Paulo Francisco
authors.initials: PF
authors.lastname: Cesar
authors.forename: Walter Gomes
authors.initials: WG
authors.lastname: Miranda
authors.forename: Humberto Naoyuki
authors.initials: HN
authors.lastname: Yoshimura
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D005898:Glass / Q000737:chemistry; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008956:Models, Chemical; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature
chemical_list: C483026:In-Ceram Alumina; D003776:Dental Porcelain; D000537:Aluminum Oxide