Just like a cast is placed around a fractured bone for protection and support, a crown offers support by covering the entire tooth. This prevents the weak tooth from flexing and being damaged even more. If a small craze line or extremely large filling is supported early enough with a crown, nerve damage may be prevented and a root canal avoided. Some cracks left unattended can fracture to the point that the tooth is rendered nonrestorable; therefore, crowns can be very important tools to saving your teeth.
If you do lose one or more teeth, a bridge may be an option for replacement. The teeth on both sides of the missing tooth/teeth space are crowned and a dummy tooth/teeth are bridged across the span. Bridges are cemented into the mouth, and therefore, are not removed by the patient.
Crowns and bridges may be made out of alloy, gold, porcelain, or a combination.
Crowns and bridges may also be placed over implants to restore dentition.