In most cases a simple filling can be used to repair small cavities, chips, fractures and other minor damage to your teeth.  In other cases, such as when there is a large cavity, an old filling that has failed, or when the tooth has had root canal therapy, a filling might not be strong enough.  In those cases, a crown or cap might be prescribed.    A crown can be thought of as a hard, protective shell of metal or porcelain that completely covers all all of the damaged tooth structure.  Unlike removable devices such as dentures, which you can take out and clean daily, crowns and bridges are cemented onto existing teeth or implants, and can only be removed by a dentist.

Besides strengthening a damaged tooth, a crown can be used to improve its appearance, shape or alignment.  A crown can also be placed on top of an dental implant to provide a tooth-like shape and structure for function. Porcelain or ceramic crowns can be matched well to the color of your natural teeth. Other materials include gold and metal alloys, acrylic and ceramic. Metal alloys are generally stronger than porcelain and may be recommended for back teeth. Porcelain bonded to a metal shell is often used because it is both strong and attractive.

Your dentist may recommend a crown to:

1. Replace a large filling when there isn't enough tooth remaining
2. Protect a weak tooth from fracturing
3. Restore a fractured tooth
4. Attach a bridge
5. Cover a dental implant
6. Cover a discolored or poorly shaped tooth
7. Cover a tooth that has had root canal treatment

A bridge may be recommended if you're missing one or more teeth. Gaps left by missing teeth eventually cause the remaining teeth to rotate or shift into the empty spaces, resulting in a bad bite. The imbalance caused by missing teeth can also lead to gum disease and temporomandibular joint (TMJ) disorders.

Bridges are commonly used to replace one or more missing teeth. They span the space where the teeth are missing. Bridges are cemented to the natural teeth or implants surrounding the empty space. These teeth, called abutments, serve as anchors for the bridge. A replacement tooth, called a pontic, is attached to the crowns that cover the abutments. As with crowns, you have a choice of materials for bridges. Your dentist can help you decide which to use, based on the location of the missing tooth (or teeth), its function, aesthetic considerations and cost. Porcelain or ceramic bridges can be matched to the color of your natural teeth.  Before either a crown or a bridge can be made, the tooth (or teeth) must be reduced in size so that the crown or bridge will fit over it properly. After reducing the tooth/teeth, your dentist will take an impression to provide an exact mold for the crown or bridge. If porcelain is to be used, your dentist will determine the correct shade for the crown or bridge to match the color of your existing teeth.  Using this impression, a dental lab then makes your crown or bridge, in the material your dentist specifies. A temporary crown or bridge will be put in place to cover the prepared tooth while the permanent crown or bridge is being made. When the permanent crown or bridge is ready, the temporary crown or bridge is removed, and the new crown or bridge is cemented over your prepared tooth or teeth.  While crowns and bridges can last a lifetime, they do sometimes come loose or fall out. The most important step you can take to ensure the longevity of your crown or bridge is to practice good oral hygiene. A bridge can lose its support if the teeth or bone holding it in place are damaged by dental disease.