The introduction of newer all-ceramic crowns has increased the popularity of restorations. Now they are stronger, more reliable and more aesthetically-pleasing than ever before. Choices include IPS Empress, a leucite-reinforced pressable porcelain that was one of the first of the newer all-ceramic crowns to be introduced to the market. Lithium disilicate crowns are even stronger and the market leader is IPS e.max. Considerably stronger than PFMs, zirconia crowns are also extremely popular, and choices include solid or monolithic zirconia and high-translucent zirconia, both of which provide excellent aesthetics.
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Leucite Reinforced Pressable Porcelain Crowns
Originally introduced 15 years ago, IPS Empress pressable crowns have a flexural strength of 160MPa and have proven to be durable and to provide excellent aesthetics. With this system, it is possible for clinicians to achieve restorations that closely replicate natural teeth. A die-shade guide is used to determine the shade of the tooth preparation, helping to decide the right tooth shade. This information allows the technician to select the correct ingot when pressing the crown. IPS Empress crowns have a high translucency which helps to transmit the shade from adjacent teeth so it is possible to obtain an exact shade match even for more difficult cases.
Lithium Disilicate Porcelain Crowns
Made from biocompatible lithium disilicate ceramic glass ingots, IPS e.max crowns are resilient to fracturing with a flexural strength of 400MPa, which is three times stronger than Empress. Crowns can be pressed or milled to offer good fit and function. With e.max, it is possible to create full-contour restorations, or to layer enamel porcelain using IPS e.max Ceram, a comprehensive layering ceramic capable of achieving highly aesthetic results.
Solid or Monolithic Zirconia
Solid or monolithic full-contour zirconia crowns are ideal for posterior restorations and are extremely strong with a flexural strength of 1200MPa. CAD/CAM-fabricated crowns offer a very precise marginal fit and are virtually unbreakable. The early monolithic zirconia crowns were often too high in value, but progressively the shades have improved considerably and can now closely match adjacent dentition. Effect shades can help to characterise the occlusal surface of the crown, and the very latest monolithic zirconia crowns offer natural translucency and opalescence. The smoothness of the surface and their durability makes monolithic zirconia crowns an appropriate choice for bruxers. If any occlusal corrections are required during fitting, monolithic zirconia is easy to polish using conventional low-speed polishing materials for porcelains. As the shade is the same throughout the crown, there is no risk of the opaque showing through, which can often be a problem when adjusting conventional PFMs.
High Translucent Zirconia
High translucent zirconia is particularly suitable for anterior crowns but can also be used for posterior crowns. It offers lifelike translucency and has a flexural strength between 590 and 720 MPA. The material is highly biocompatible and promotes a healthy tissue response as well as having a natural aesthetic. Once in the mouth, high-translucent zirconia transmits the colour of adjacent teeth, therefore these restorations will blend in beautifully. High-translucent zirconia can be used in monolithic restorations or it may be layered. Its translucency is due to the way the material is processed, minimising the effects of impurities and structural defects, which could otherwise affect its ability to allow light through. When impurities are present, it can cause light absorption and when structural defects are present it can scatter light.
With today’s choice of all-ceramic materials, it should be relatively straightforward for clinicians to choose the correct type of crown. Our experienced technical team can always offer advice on individual cases based on our in-depth knowledge of these materials.
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