Subcritical crack growth in porcelains, glass-ceramics, and glass-infiltrated alumina composite for dental restorations.
The objective was to compare fracture toughness (K(Ic)), stress corrosion susceptibility coefficient (n), and stress intensity factor threshold for crack propagation (K(I0)) of two porcelains [VM7/Vita (V) and d.Sign/Ivoclar (D)], two glass-ceramics [Empress/Ivolcar (E1) and Empress2/Ivlocar (E2)] and a glass-infiltrated alumina composite [In-Ceram Alumina/Vita (IC)]. Disks were constructed according to each manufacturer's processing method, and polished before induction of cracks by a Vickers indenter. Crack lengths were measured under optical microscopy at times between 0.1 and 100 h. Specimens were stored in artificial saliva at 37 degrees C during the whole experiment. K(Ic) and n were determined using indentation fracture method. K(I0) was determined by plotting log crack velocity versus log K(I). Microstructure characterization was carried out under SEM, EDS, X-ray diffraction and X-ray fluorescence. IC and E2 presented higher K(Ic) and K(I0) compared to E1, V, and D. IC presented the highest n value, followed by E2, D, E1, and V in a decreasing order. V and D presented similar K(Ic), but porcelain V showed higher K(I0) and lower n compared to D. Microstructure features (volume fraction, size, aspect ratio of crystalline phases and chemical composition of glassy matrix) determined K(Ic). The increase of K(Ic) value favored the increases of n and K(I0).
Gonzaga
Carla Castiglia
CC
Department of Biomaterials and Oral Biochemistry, School of Dentistry, University of São Paulo, Sao Paulo, Brazil.
Yoshimura
Humberto Naoyuki
HN
Cesar
Paulo Francisco
PF
Miranda
Walter Gomes
WG
D000537:Aluminum Oxide / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D003343:Corrosion; D003764:Dental Materials / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013052:Spectrometry, X-Ray Emission; D013314:Stress, Mechanical; D013499:Surface Properties; D014961:X-Ray Diffraction
D003764:Dental Materials; D003776:Dental Porcelain; C023506:Glass ceramics; D000537:Aluminum Oxide