Crowns are the ideal restoration for teeth that have broken, or have been weakened by decay or a very large filling. Crowns can be made from a variety of different materials and are fixed in place with special dental adhesive. Crowns completely cover and protect teeth and restore them to their proper shape and size.
Porcelain on metal crowns is often used for back teeth. The metal gives strength and support to the porcelain but the metal layer reduces the translucency of the crown making it appear opaque and duller than the natural tooth. These crowns are normally considered cosmetically unacceptable for front teeth and unless there is a porcelain shoulder on the crown a dark line tends to develop after a few years where the tooth meets the gum.
Gold crowns may be white or gold in colour. Gold is alloyed with other metals to increase its strength, which makes it a very hardwearing restoration.
Full porcelain crowns are normally used for front teeth because they look very natural and appear slightly translucent like ordinary teeth.
After the area has been numbed the tooth that is to be crowned is prepared by grinding it to a shape that is able to support the new crown. An impression is then made of the reduced tooth and gum. A temporary crown is usually placed on top of the reduced tooth at this stage. The lab then makes the permanent crown from the impression that has been taken. 4-5 days later the temporary crown is removed and the permanent new crown is fitted.
A bridge allows one or more missing teeth to be replaced without using a denture or dental implant. The missing tooth is replaced with a pontic tooth, which is fused between two crowns that are permanently attached to the adjacent teeth. So the new tooth is held in place by being attached on each side to an adjacent crowned tooth.
The disadvantage of bridges is that the teeth either side of the space have to be crowned in order to accept the bridge. However without a bridge or implant the unsupported teeth will tend to tilt toward the gap altering the alignment of the occlusion and reducing the efficiency of the bite.