Method: The nano-composite powders (MACZ-100, Matsushita Electric Works, Osaka, Japan) were pressed to a cylindrical rod using CIP. After firing at 1450˚C for 2 hr, identically shaped three-unit frameworks were machined by a dental milling system (hiCut, Hint-Els, Griesheim, Germany). To compare with conventional Y-TZP, 3 mol% yttria stabilized TZP powders (TZ-3YB-E, Tosoh, Tokyo, Japan) were also pressed, fired at 1350˚C for 6 hr, and machined by the same method. The framework corresponds to the situation of a three-unit bridge from the second premolar to the second molar of the maxilla. These bridge-frameworks were fixed on a metal post (16.4 mm in span length) without any cementing and loaded on the center of the bridges at 0.5 mm/min in cross-head speed with a metal rod rounded 8 mm in diameter. Ten frameworks of each were measured and analyzed by Weibull statistics.
Results: Weibull analysis demonstrated that the fracture strengths of the Ce-TZP/Al2O3 nano-composite and the Y-TZP showed similar Weibull muduli, 2.9 and 3.1, respectively, whereas the characteristic strengths of the Ce-TZP/Al2O3 nano-composite (7613 N) was much higher than that of the Y-TZP (5121 N), indicating a better reliability against the load-bearing.
Conclusion: It is concluded that the Ce-TZP/Al2O3 nano-composite can be safely applied to dental restoratives such as all-ceramic bridges.