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.