Impact of Implant Abutment on Optical Properties of Zirconia Crowns

Esthetic dental restorations need to match the size, shape, shade, texture and translucency of the natural teeth they are replacing. Although porcelain fused to ceramic restorations have a long history of clinical success, they have metal substructures which may lead to non-optimal esthetic outcomes. Ceramic restorations may be designed with translucent cores with optical properties matching natural dentitions. Increasing esthetic demands have led to widespread use of all- ceramic restorations. Dental ceramics like feldspathic porcelain and glass ceramic provide acceptable esthetic results against a non-discolored abutment due to their light transmission. However, brittle nature of ceramics can cause fatigue failure after cyclic loading. Zirconia has been introduced to dentistry as an alternative material due to its excellent mechanical properties. Zirconia exhibits a tetragonal-to-monoclinic phase transformation on cooling, which is accompanied by a 3% to 5% increase in volume. While this imposes residual compressive stresses and consequent transformation toughening, it also results in microcracking and compromised mechanical properties.