Weibull analysis and flexural strength of glass-infiltrated alumina composite machined by CAD/CAM
Sun, Q.; Bai, B.; Hao, Y.-q.; Wen, L.; Sun, J.-n.; Ai, H.-j.
Shanghai Kou Qiang Yi Xue 13(6): 549-552
2004
ISSN/ISBN: 1006-7248 PMID: 15619703 Document Number: 567983
To explore the structural reliability of machined infiltrated ceramic made from ultrafine alumina powder for dental CAD/CAM by means of flexural strength together with Weibull analysis. Ultrafine grain-sized alumina powder made from ammonium aluminum sulfate was sintered into one kind of porous machined ceramic block. After being infiltrated by lanthanum glass powder, a glass infiltrated alumina composite was produced. Thirty bar specimens were prepared. The flexural strength was measured with the three-point bending test. The fracture stress values were analyzed by Weibull analysis to determine the Weibull modulus values(m). The strength values at failure probabilities of 1% and 5% failure were also calculated. X ray diffraction analysis (XRD) and scanning electron microscopy (SEM) analysis were conducted. The mean flexural strength and standard deviation were (375.5+/-66.88) MPa coupled with Weibull modulus of 6.2. Strength values at failure probability of 1% and 5% were 191.79 MPa and 249.83 MPa, respectively. The micrograph under SEM indicated the prefabricated sintered alumina block retained a structure of continuous three-dimensional open pores, whereas the composite characterized itself as a pore-free structure after glass infiltration. XRD indicated the major crystal phase was alpha-alumina. The average fracture strength can not be used reliably as a design parameter for brittle all-ceramic crown materials. Compared with the average fracture strength alone, the use of flexure strength test combined with the Weibull analysis as a method of predicting survival rates from the strength data could be favorable in identifying the failure mechanisms involved in ceramic crown fracture, which would result in an improved validation of the strength data.