Strength and reliability of surface treated Y-TZP dental ceramics

TLDR

Standard Y‑TZP ceramics are more resistant in alkaline than acidic environments, with grain size strongly influencing diffusion‑controlled transformation. This study evaluated how dental grinding and sandblasting affect biaxial flexural strength and Weibull modulus of 3 mol % yttria Y‑TZP ceramics. The authors examined the susceptibility of pristine and mechanically treated Y‑TZP to low‑temperature degradation under conditions used for chemical solubility testing. Grinding lowered mean strength and Weibull modulus, sandblasting increased strength but reduced reliability; the finest‑grained material had the highest strength yet was least damage tolerant; acid extraction caused substantial tetragonal‑to‑monoclinic transformation without extensive microcracking; and an alumina‑containing Y‑TZP grade exhibited superior damage tolerance and acidic stability, suggesting its promise for dental applications.

Abstract

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.