Jensen26
26-11-07, 03:59 AM
Ceramics are very hard and durable glass based materials that can only be formed outside the mouth. Great strides have been made over the last few years to speed the fabrication process and to reduce their brittleness. Ceramics of one form or another are used for almost all of our crown restorative procedures.
Classically, ceramics can be very beautiful but rather brittle. The most common way of using them in the mouth has been where they are enameled to a cast metal substructure. In this way one gets the strength of a metal framework with the esthetics of ceramic. However, it can sometimes be tough to mask the metal framework, particularly at the margin.
The primary weakness of ceramics comes from porosities and inclusions that get included as the ceramic is built up in layers. Although, it is possible to find ceramics with have higher strength, the fabrication process has always been the weak link. That is until now. With the CEREC computerized scanning, design and milling technology it is now possible to take a high resolution picture of the tooth, to design the restoration on the computer and to mill the final shape of the restoration right in the office from a high strength block of ceramic. This way there are no inclusions or porosities in the ceramic and the restorations are much stronger.
First to produce Ceramic fillings (http://www.rajkrishnan.com/) and restorations that can be fitted in the same session that the tooth is prepared. This is great for the replacement of old silver amalgam restorations. These ceramic restorations are stronger and much more durable than plastic or composite fillings. Second, for larger cases, it allows for the production of strong ceramic frameworks which replace the metal substructures traditionally used. On these high strength ceramic frameworks additional layers of ceramic are fused to gain optimal esthetics.
There are limitations to this system. For example, it is not very easy to splint teeth together or to construct bridgework. However, fewer and fewer bridges are being placed these days because more and more missing teeth are being replaced by implants.
Classically, ceramics can be very beautiful but rather brittle. The most common way of using them in the mouth has been where they are enameled to a cast metal substructure. In this way one gets the strength of a metal framework with the esthetics of ceramic. However, it can sometimes be tough to mask the metal framework, particularly at the margin.
The primary weakness of ceramics comes from porosities and inclusions that get included as the ceramic is built up in layers. Although, it is possible to find ceramics with have higher strength, the fabrication process has always been the weak link. That is until now. With the CEREC computerized scanning, design and milling technology it is now possible to take a high resolution picture of the tooth, to design the restoration on the computer and to mill the final shape of the restoration right in the office from a high strength block of ceramic. This way there are no inclusions or porosities in the ceramic and the restorations are much stronger.
First to produce Ceramic fillings (http://www.rajkrishnan.com/) and restorations that can be fitted in the same session that the tooth is prepared. This is great for the replacement of old silver amalgam restorations. These ceramic restorations are stronger and much more durable than plastic or composite fillings. Second, for larger cases, it allows for the production of strong ceramic frameworks which replace the metal substructures traditionally used. On these high strength ceramic frameworks additional layers of ceramic are fused to gain optimal esthetics.
There are limitations to this system. For example, it is not very easy to splint teeth together or to construct bridgework. However, fewer and fewer bridges are being placed these days because more and more missing teeth are being replaced by implants.