Strength and reliability of surface treated Y-TZP dental ceramics

This work was undertaken to evaluate the effects of dental grinding and sandblasting on the biaxial flexural strength and Weibull modulus of various Y-TZP ceramics containing 3 mol% yttria. In addition, the susceptibility of pristine and mechanically treated materials to low-temperature degradation under the conditions adopted for testing the chemical solubility of dental ceramics was investigated. The results revealed that surface grinding and sandblasting exhibit a counteracting effect on the strength of Y-TZP ceramics. Dental grinding lowered the mean strength and Weibull modulus, whereas sandblasting provided a powerful method for strengthening, but at the expense of somewhat lower reliability. The finest-grained material exhibited the highest strength after sintering, but it was less damage tolerant than tougher, coarse-grained materials. Upon extraction with the acetic acid solution and the ammonia solution, a significant amount of tetragonal zirconia had transformed to monoclinic, but extensive microcracking and attendant strength degradation had not yet occurred. Standard grade Y-TZP ceramics are more resistant in an alkaline than in an acidic environment, and there was a strong grain-size dependence of the diffusion-controlled transformation. Since a special Y-TZP grade containing a small amount of alumina exhibited the highest damage tolerance and superior stability in an acidic environment, this material shows considerable promise for dental applications. (C) 2000 John Wiley & Sons, Inc.