Since the late 90s the use of zirconia based all-ceramic restorations increases. Many manufacturing steps are necessary, like pre-sintering, soft machining (pre-sintered condition), sintering and hard machining (fully sintered) in combination with a final staining or veneering step. All these techniques, especially hard machining, are associated with the production of flaws in different scales, in conjunction with thermal and residual stresses and phase transformations. These are inter alia capable to induce failure. This work investigates the impact of hard machining on the material properties and attempts to establish a correlation to failure. © 2016 Published by Elsevier B.V.