Effect of ion exchange on hardness and fracture toughness of dental porcelains.
The objective of this study was to evaluate the effect of ion exchange, IE, on fracture toughness K(Ic) and hardness H of five dental porcelains with different microstructures: B, Ceramco II/Dentstply; C, Finesse/Dentsply; Cb, Cerabien/Noritake; D, d.Sign/Ivoclar; V, Vitadur Alpha/Vita. Specimens were sintered according to manufacturers' instructions, n = 10. Vickers indentations were made on specimens' surfaces before and after IE to calculate H and K(Ic). IE treatment consisted in coating the surface of the specimen with slurry of KNO(3) and distilled water, with subsequent drying for 20 min at 150 degrees C and heating for 30 min at 450 degrees C. Microstructural analysis was also performed. The measured leucite contents were 22, 15, 6, 0, and 0% for porcelains B, D, C, Cb, and V, respectively. Porcelains C, Cb, D, and V showed a significant increase in hardness after IE. Hardness of porcelain B was not affected by IE. Materials with lower leucite content tended to present higher increases in hardness after ion exchange. Ion exchange significantly increased K(Ic) between 64 and 156% of 4 out of 5 porcelains studied. Porcelain B was the only one to present a decrease in fracture toughness after ion exchange.
Cesar
Paulo Francisco
PF
Department of Dental Materials, School of Dentistry, University of São Paulo, São Paulo, Brazil. paulofc@usp.br
Gonzaga
Carla Castiglia
CC
Miranda
Walter Gomes
WG
Yoshimura
Humberto Naoyuki
HN
D000538:Aluminum Silicates / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D006244:Hardness; D006801:Humans; D007474:Ion Exchange; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning
D000538:Aluminum Silicates; D003776:Dental Porcelain; C078519:leucite