We have all seen the unsightly black line that appears when the gum receeds away from crown margins. This darkness in the root next to the crown is due to light being reflected from the metal shell which forms the core of most modern crowns. It is this shell that provides the strength of the crown and porcelain is then bonded onto it to provide as aesthetic result as possible. The dullness often seen in crowns is due to the need to put an opaqueing layer to hide the metal core. Light hits this layer and does not reflect well leaving a life-less visual impression. An exception to this is the use of high quality gold metal cores where the yellow gold can mimic the natural colour of the dentine and provide warmth to the finished crown, especially when the adjacent teeth are darker.
|
|
It is possible to make all porcelain jacket crowns but only where there is little or no load, for example when a patient has prominent front teeth. Modern dentistry solves this problem by adapting the preparation of the tooth and providing a white alumina/leucite core which is very hard and bonds well to porcelain. There are several systems in use but our current preference is for the Cercon system.
The Cercon system involves making a machined core for the crown. This has the advantage of being very strong but has the advantage over other systems in that the core is transluscent allowing the natural colour of the tooth to reflect though the crown.
Normally, we ask the patient to attend the laboratory for shading to allow the technician to include small nuances of shade and subtleties of shape to ensure a natural aesthetic result. |
