Crowns and bridges have traditionally been made with feldspathic porcelain. It is a beautiful material to work with, but it is not as strong as newer ceramic materials like zirconia. We offer zirconia bridges and crowns as well as ones made from feldspathic porcelain. We also offer e.max crowns and bridges, which combine the beauty of feldspathic porcelain with the strength of zirconia. We’ll discuss them here.
Simply put, zirconia is a type of ceramic. Its tensile strength has earned it a place in the aerospace and other high-tech industries, along with the nickname ceramic steel. And a bridge is a dental restoration that can bridge gaps where one or more teeth are missing. The two adjacent teeth are prepared to receive crowns, and the prosthetic tooth is suspended between them.
Feldspathic porcelain alone is not strong enough to be used for a bridge in the back of the mouth where chewing pressures are greater. So bridges have traditionally been made from porcelain that was fused to a metal base. The result was restorations that often looked dull and lifeless because they had to be opaque enough to cover the metal base. And the crowns always developed a telltale dark line at the gumline.
Zirconia bridges placed with newer bonding technology are so strong that there is no need for a metal framework. And the results are restorations that have the translucency, color variation, and sparkle of real teeth.
While feldspathic crowns and bridges are created by stacking and firing many different layers of porcelain, zirconia crowns and bridges are milled from a single small piece of ceramic. Zirconia also virtually eliminates the risk of allergic reactions because it is very biocompatible. In fact, doctors use very similar materials in hip replacements. And because it is so strong, zirconia can be milled to extremely thin tolerances, offering a precise fit where the border of the restoration meets the tooth enamel.
One brand of crowns and bridges that uses a zirconia framework is e.max, a product of the Ivoclar company. The first step in making one of these crowns or bridges is to make the crown or bridge out of zirconia. Since zirconia has some esthetic limitations, the front part of the restoration is prepared by shaving a thin layer from the front. Feldspathic porcelain is then baked onto the front. This gives the ceramist the ability to bake in a depth of color as well as subtle highlights and variations.