Crown and Bridge
Both crowns and bridges strengthen weakened teeth by covering and surrounding them 360o. Crowns cover a single tooth. Bridges cover multiple teeth, replacing any missing teeth in between.
When a tooth has been weakened by root canal therapy or a large filling, it should be covered with a crown. The photo below shows a tooth that should have had a crown after a root canal. Because it didn’t get the needed crown it cracked and split under chewing pressure. The red line shows the extent of the crack; it broke off a cusp and split the tooth in half between the roots. In this example the split could not be repaired and the tooth was extracted. If it had a crown soon after the root canal, it wouldn’t have been lost.
When crown is made for a tooth it is first numbed and shaped to have an even taper from top to bottom. This shape will allow the crown to slide down and fit snugly over the tooth. An impression of the tooth is made, and a temporary crown covers the tooth while the dental lab makes the permanent crown. Later the temporary crown is removed and the permanent crown is cemented. Crowns can be made of porcelain (for superior esthetics) or of gold (on back teeth where chewing and grinding forces are greater). Crowns last on average 10 years or more.
A bridge replaces missing teeth when there are existing teeth on both sides of the space. Crowns cover these adjacent teeth with the replacement teeth attached in between the crowns. Because a bridge is a single piece of porcelain connecting the teeth, you can’t floss a bridge like you would the other teeth. Floss must be passed under the bridge from the side to keep gums healthy and prevent decay on the roots of the teeth that support the bridge.
The patient shown on the right is missing several front teeth. Three teeth shown here have been prepared to support a porcelain bridge.