Zirconia as a biomaterial for dental use

Abstract

Due to the biocompatibility and mechanical properties that are more than satisfying, zirconia has been successfully used in recent years as a preferred dental biomaterial. Zirconia is a polymorphic material that occurs in three temperature-dependant forms that are: monoclinic (room temperature to 1170 C), tetragonal (1170 C–2370 C) and cubic (2370 C – up to melting point)1. However, when stabilizing oxides such as magnesia, ceria, yttria and calcium are added to zirconia, the tetragonal phase is retained in a metastable condition at room temperature, enabling a phenomenon called transformation toughening to occur. Y-TZP Ceramics have a unique characteristic of „Stress Induced Transformation” that gives them superior mechanical properties compared with other ceramics. Scientific studies suggest that zirconium dioxide does not relieve allergens and other non-compatible substances in the mouth. In addition, it is excellently tolerated by soft tissues. Successfully used for more than 20 years in medicine-surgery and orthopedics, and now has already entered the dental medicine. Zirconia cores are generally covered with ceramic because of the opaque color of the zirconia. The incrustation of zirconia with ceramic is giving the restoration a more natural and aesthetic look but there are registered incidences of chipping. This is why the more translucent zirconia (full-contour-without ceramic incrustation ) restorations are used nowadays.