Correlation between fracture toughness and leucite content in dental porcelains.
OBJECTIVES: To determine the correlation between fracture toughness and leucite content in dental porcelains. The mechanisms by which leucite influences the fracture toughness of dental porcelains were also investigated. METHODS: Six porcelains were tested: A (Ceramco I/Dentsply), B (Ceramco II/Dentsitply), C (Finesse/Dentsply), D (d.Sign/Ivoclar), Cb (Cerabien/Noritake) and V (Vitadur Alpha/Vita). Bar-shaped specimens were produced, and their fracture toughness was determined by means of the single-edge precracked beam (SEPB) method. The test consisted of fracturing the specimen after a precrack was generated by a bridge-anvil device. KIc was calculated based on fracture force and size of the precrack. Microstructural analysis and determination of the leucite volume fraction were performed on polished specimens etched with 2% HF for 15s by means of scanning electron microscopy. Fractographic analysis was performed on fracture surfaces. RESULTS: Porcelains A and B presented the highest leucite contents (22%) and similar KIc values (1.23 and 1.22 MPa m1/2, respectively), significantly higher than the other materials. Porcelains C and D presented similar K(Ic) values (0.81 and 0.93 MPa m1/2, respectively), but different leucite contents (6 and 15%, respectively). Porcelain D presented higher KIc compared to porcelains Cb and V (0.71 and 0.75 MPa m1/2, respectively), which presented similar values and the lowest leucite contents (0%). Fractographic analysis showed that porcelains with higher leucite content presented higher incidence of crack deflection. CONCLUSIONS: For the materials evaluated in this study, the leucite content was directly related to KIc. The main toughening mechanism observed was crack deflection around leucite particles and clusters.[1]References
- Correlation between fracture toughness and leucite content in dental porcelains. Cesar, P.F., Yoshimura, H.N., Miranda Júnior, W.G., Okada, C.Y. Journal of dentistry. (2005) [Pubmed]
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