Microstructural features, physicο-mechanical properties, and wear behavior of dental translucent polychromic multilayer zirconia of hybrid composition prepared by milling technology

Abstract

Objective: The present study determined the mechanical properties and the wearbehavior, as results of the micro(nano)structure, of the enamel, transition, and den-tine layers, which comprise the polychromic multilayer zirconia materials of hybridcomposition fabricated by milling technology.Materials and Methods:Prismatic blocks were fabricated from two commercialpre-sintered dental polychromic multilayer zirconia materials of hybrid composi-tion, IPS e.max ZirCAD Prime (medium andhigh translucency, from the dentineto the incisal layer) and 3D Pro ML (translucency gradient, from the dentine tothe incisal layer) by milling technique, and then, cut into 3 distinct parts to sepa-rate the enamel, transition, and dentine layers. The samples were sintered, ther-mally treated (similarly to the glazing procedure), and polished forcharacterization. Their microstructure, mechanical properties (determined bynanoindentation and microhardness), andwear behavior (evaluated by scratchtest), were examined.Results:The produced materials had a homogeneous and dense nanostructure,where the grain size decreased from the enamel to dentine layer. The mechanicalproperties also decreased from the enamel to dentine layer. However, the threelayers manifested similar dynamic friction coefficient.Conclusion:The differences in the above properties in the three layers negligiblyinfluenced the wear behavior of the entire multilayer zirconia material.Clinical Significance:The properties of dental restorations produced from poly-chromic multilayer zirconia of hybrid composition by milling technology(i.e., strong, non-fragile, and esthetic materials), anticipate good performance inoral cavity