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Influence of leucite content on slow crack growth of dental porcelains

2008; Elsevier BV; Volume: 24; Issue: 8 Linguagem: Inglês

10.1016/j.dental.2008.01.003

1879-0097

Paulo Francisco César, Fabiana N. Soki, Humberto Naoyuki Yoshimura, Carla Castiglia Gonzaga, V. I. Styopkin,

Dental Erosion and Treatment

To determine the stress corrosion susceptibility coefficient, n, of seven dental porcelains (A: Ceramco I; B: Ceramco-II; C: Ceramco-III; D: d.Sign; E: Cerabien; F: Vitadur-Alpha; and G: Ultropaline) after aging in air or artificial saliva, and correlate results with leucite content (LC). Bars were fired according to manufacturers' instructions and polished before induction of cracks by a Vickers indenter (19.6 N, 20 s). Four specimens were stored in air/room temperature, and three in saliva/37 °C. Five indentations were made per specimen and crack lengths measured at the following times: ∼0; 1; 3; 10; 30; 100; 300; 1000 and 3000 h. The stress corrosion coefficient n was calculated by linear regression analysis after plotting crack length as a function of time, considering that the slope of the curve was [2/(3n + 2)]. Microstructural analysis was performed to determine LC. LC of the porcelains were 22% (A and B); 6% (C); 15% (D); 0% (E and F); and 13% (G). Except for porcelains A and D, all materials showed a decrease in their n values when stored in artificial saliva. However, the decrease was more pronounced for porcelains B, F, and G. Ranking of materials varied according to storage media (in air, porcelain G showed higher n compared to A, while in saliva both showed similar coefficients). No correlation was found between n values and LC in air or saliva. Storage media influenced the n value obtained for most of the materials. LC did not affect resistance to slow crack growth regardless of the test environment.