Cesar Paulo F, Yoshimura Humberto N, Miranda Júnior Walter G, Okada Cristina Y
Department of Dental Materials, School of Dentistry, University of São Paulo, Brazil.
J Dent. 2005 Oct;33(9):721-9. doi: 10.1016/j.jdent.2005.02.001. Epub 2005 Mar 25.
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.
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.
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.
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.
确定牙科陶瓷中断裂韧性与白榴石含量之间的相关性。同时研究白榴石影响牙科陶瓷断裂韧性的机制。
测试了六种陶瓷：A（Ceramco I/登士柏）、B（Ceramco II/登士柏）、C（Finesse/登士柏）、D（d.Sign/义获嘉）、Cb（Cerabien/ Noritake）和V（Vitadur Alpha/维他）。制作了条形试样，并通过单边预裂纹梁（SEPB）法测定其断裂韧性。该测试包括在通过桥砧装置产生预裂纹后使试样断裂。基于断裂力和预裂纹尺寸计算Kıc。通过扫描电子显微镜对用2%氢氟酸蚀刻15秒的抛光试样进行微观结构分析和白榴石体积分数的测定。对断裂表面进行断口分析。
陶瓷A和B的白榴石含量最高（22%），且Kıc值相似（分别为1.23和1.22 MPa m1/2），显著高于其他材料。陶瓷C和D的K(Ic)值相似（分别为0.81和0.93 MPa m1/2），但白榴石含量不同（分别为6%和15%）。与陶瓷Cb和V（分别为0.71和0.75 MPa m1/2）相比，陶瓷D的Kıc更高，陶瓷Cb和V的Kıc值相似且白榴石含量最低（0%）。断口分析表明，白榴石含量较高的陶瓷裂纹偏转发生率较高。
对于本研究中评估的材料，白榴石含量与Kıc直接相关。观察到的主要增韧机制是白榴石颗粒和团聚体周围的裂纹偏转。
