Influence of leucite content on slow crack growth of dental porcelains

• Published in: Dental materials 2008-08, Vol.24 (8), p.1114-1122
• Main Authors: Cesar, Paulo F, Soki, Fabiana N, Yoshimura, Humberto N, Gonzaga, Carla C, Styopkin, Victor
• Format: Article
• Language: English
• Subjects: Advanced Basic Science; Air; Algorithms; Aluminum Silicates - analysis; Aluminum Silicates - chemistry; Apatites - analysis; Apatites - chemistry; Dental porcelain; Dental Porcelain - analysis; Dental Porcelain - chemistry; Dentistry; Fracture toughness; Glass - analysis; Glass - chemistry; Humans; Materials Testing; Mechanical properties; Microscopy, Electron, Scanning; Microstructure; Saliva, Artificial - chemistry; Slow crack growth; Stress, Mechanical; Surface Properties; Temperature; Time Factors
• ISSN: 0109-5641; 1879-0097
• DOI: 10.1016/j.dental.2008.01.003

Abstract Objectives 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). Methods 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/(3 n + 2)]. Microstructural analysis was performed to determine LC. Results 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. Significance 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.