Yttria-stabilized zirconia, also known simply as zirconia, is a very hard ceramic that is used as a strong base material in some full ceramic restorations.
Zirconia is relatively new in dentistry and the published clinical data is correspondingly limited.
The zirconia used in dentistry is zirconium oxide which has been stabilized with the addition of yttrium oxide.
Yttria-stabilized zirconia is also known as YSZ.

The zirconia substructure (core) is usually designed on a digital representation of the patient's mouth, which is captured with a three-dimensional digital scan of the patient, impression, or model.
The core is then milled from a block of zirconia in a soft pre-sintered state.
Once milled, the zirconia is sintered in a furnace where it shrinks by 20% and reaches its full strength of 850MPa to 1000MPa.
The zirconia core structure can be layered with tooth tissue-like feldspathic porcelain to create the final color and shape of the tooth.
Because bond strength of layered porcelain fused to zirconia is not strong; chipping of the conventional veneering ceramic frequently occurs, crowns and bridges are nowadays increasingly made with monolithic zirconia crowns produced from a color and structure graded zirconia block, and coated with a thin layer of glaze stains.
Esthetic prosthetic restorations, with natural reflection, color from within and color gradients influenced by the internal dentinal core anatomy can best be accomplished by veneered zirconia, rather than with crowns of monolithic zirconia.
In the production of dental restorations specifically made for one patient, dental technicians with their problem-solving skills, dexterity and cognitive skills are until recently the only way to provide the required esthetics, individuality and artistry with porcelain.
Fear for chipping of conventional mono glass component zirconia porcelains on the longer term and price pressure on manual application of porcelain, are possible drivers for the monolithic zirconia restorations.
However, by the application of multi-glass component porcelain chipping is no longer an issue, especially with prosthetic mimetic restorations where the crown follows a model of the natural tooth in two layers: a histo-anatomic dentin layer mimicking the dentin shape of the dentition of the patient and an enamel layer.
These restorations that mimic the structure of natural teeth by cognitive design of the dentin core present a new production paradigm to fabricate natural restorations of veneered zirconia using a high strength porcelain with CAD/CAM.
These crowns are produced with a core of tooth-colored tetragonal zirconia, on which a high strength translucent porcelain layer has been applied and subsequently milled to size.
In the subtle cooperation between the dentin-colored zirconia and the veneering porcelain, the zirconia shines through the translucent porcelain layer, all the more as the porcelain layer is thinner.
This creates the natural color dynamics with color "from the inside" as found in natural elements, instead of color "on the outside", with monolithic zirconia.
As a result, the natural tooth, in terms of esthetics and hardness, is approached closer than crowns made from solid monolithic zirconia.
This implies that the histo-anatomic dentin core is the key to esthetic crowns.

Zirconia is the hardest known ceramic in industry and the strongest material used in dentistry, it has to be fabricated using a CAD/CAM process but not the conventional manual dental technology.
Because of this monolithic zirconia does not wear itself as the normal vertical wear of 25-75 microns of natural enamel and porcelain, there are no clinical data on the fact whether as a consequence too high zirconia crowns will damage opposing dentition on the longer term.
Although in two body wear testing of monolithic, veneered and glazed zirconia and their corresponding enamel antagonists showed similar wear, at least twice as much extensive, and branched enamel microcracks were observed in the samples opposing monolithic zirconia.
Yttria-stabilized zirconia, also known simply as zirconia, is a very hard ceramic that is used as a strong base material in some full ceramic restorations. Zirconia is relatively new in dentistry and the published clinical data is correspondingly limited. The zirconia used in dentistry is zirconium oxide which has been stabilized with the addition of yttrium oxide. Yttria-stabilized zirconia is also known as YSZ.
The zirconia substructure (core) is usually designed on a digital representation of the patient's mouth, which is captured with a three-dimensional digital scan of the patient, impression, or model. The core is then milled from a block of zirconia in a soft pre-sintered state. Once milled, the zirconia is sintered in a furnace where it shrinks by 20% and reaches its full strength of 850MPa to 1000MPa. The zirconia core structure can be layered with tooth tissue-like feldspathic porcelain to create the final color and shape of the tooth. Because bond strength of layered porcelain fused to zirconia is not strong; chipping of the conventional veneering ceramic frequently occurs, crowns and bridges are nowadays increasingly made with monolithic zirconia crowns produced from a color and structure graded zirconia block, and coated with a thin layer of glaze stains. Esthetic prosthetic restorations, with natural reflection, color from within and color gradients influenced by the internal dentinal core anatomy can best be accomplished by veneered zirconia, rather than with crowns of monolithic zirconia. In the production of dental restorations specifically made for one patient, dental technicians with their problem-solving skills, dexterity and cognitive skills are until recently the only way to provide the required esthetics, individuality and artistry with porcelain. Fear for chipping of conventional mono glass component zirconia porcelains on the longer term and price pressure on manual application of porcelain, are possible drivers for the monolithic zirconia restorations. However, by the application of multi-glass component porcelain chipping is no longer an issue, especially with prosthetic mimetic restorations where the crown follows a model of the natural tooth in two layers: a histo-anatomic dentin layer mimicking the dentin shape of the dentition of the patient and an enamel layer. These restorations that mimic the structure of natural teeth by cognitive design of the dentin core present a new production paradigm to fabricate natural restorations of veneered zirconia using a high strength porcelain with CAD/CAM. These crowns are produced with a core of tooth-colored tetragonal zirconia, on which a high strength translucent porcelain layer has been applied and subsequently milled to size. In the subtle cooperation between the dentin-colored zirconia and the veneering porcelain, the zirconia shines through the translucent porcelain layer, all the more as the porcelain layer is thinner. This creates the natural color dynamics with color "from the inside" as found in natural elements, instead of color "on the outside", with monolithic zirconia. As a result, the natural tooth, in terms of esthetics and hardness, is approached closer than crowns made from solid monolithic zirconia. This implies that the histo-anatomic dentin core is the key to esthetic crowns.
Zirconia is the hardest known ceramic in industry and the strongest material used in dentistry, it has to be fabricated using a CAD/CAM process but not the conventional manual dental technology. Because of this monolithic zirconia does not wear itself as the normal vertical wear of 25-75 microns of natural enamel and porcelain, there are no clinical data on the fact whether as a consequence too high zirconia crowns will damage opposing dentition on the longer term. Although in two body wear testing of monolithic, veneered and glazed zirconia and their corresponding enamel antagonists showed similar wear, at least twice as much extensive, and branched enamel microcracks were observed in the samples opposing monolithic zirconia.
Crown (dentistry)