crowns and bridges
Imagine doing all your chewing on just a few teeth. This is what often happens when one or more teeth are worn, damaged, missing, or just been so heavily filled they can no longer do their job. The health of other teeth can then be threatened. If teeth are not restored or replaced, this can progressively lead to bite changes, increased loading, wear and fracture of adjacent teeth, and even jaw joint and muscle problems, not to mention aesthetic problems.
what are they?
A crown is a capping that fits over and around a tooth to protect it. Some tooth structure must be removed to make room for it but, once it is cemented into position, it usually makes the tooth much stronger and better looking than it was before. Crowns can also be done on implants. A bridge is where a tooth is missing and crowns on the adjacent teeth or implants (the "abutments") are used to support the false tooth (the "pontic") or teeth in between. Bridges restore aesthetics and stability after a tooth is lost. Liz (pictured above) had some very old crowns that looked very obvious before they were replaced.
materials used
There are many materials available today and whether one is recommended over another depends on the patient's specific needs.
They can include:
- Metal ceramic (porcelain fused to high noble, semi-precious or non-precious alloy). Our practice only uses high noble alloys in its crowns.
- All ceramic. These have better aesthetics than metal ceramic but slightly reduced fracture resistance. The patient whose teeth you see above wanted metal free ceramic crowns that matched her highly bleached lower teeth.
- Gold. The beauty of gold is it will not fracture, even in the most severe bruxer. It is the best material from a functional point of view but these days is generally used only at the back of the mouth in patients with a history of breakage of other materials.
- Composite resin or acrylic resin. These are only for provisional crowns.
reasons for having them
- Large, worn, fractured or defective fillings. Crowns can work where there is not enough tooth structure to support a normal filling. Once a tooth is 70% filled, it probably needs a crown.
- Fractured teeth caused by cracks, trauma, large unsupported fillings or habitual or accidental grinding and clenching. A crown can physically bind the cusps together preventing them from flexing under load. Of course it also makes a broken tooth look good again.
- Endodontically treated teeth (teeth which have had a root canal therapy). If a tooth is not restored promptly bacteria can contaminate the root canal therapy or cause recurrent decay. Molars and premolars that are endodontically treated are at risk of root fracture. An appropriate crown can give them an excellent long term prognosis.
- Missing teeth. Shifting and tipping of adjacent teeth can lead to changes in the jaw muscles, bones and joints, and make chewing and cleaning harder.
stages
Preparation (usually one but often two appointments)
- Removal of existing filling materials from the tooth or teeth to be crowned.
- Core or foundation buildup (composite resin)
- Crown preparation (removal of 1-1.5mm of tooth structure from the top and sides of the tooth)
- Provisional crown or bridge construction
- Detailed impression
- Impression of the opposing teeth, face bow and bite registration
- Cementing of the provisional crown or bridge
Issue (usually 3-4 weeks later, sometimes two appointments if modifications are required)
- Removal of the provisional crown or bridge
- Cleaning of the tooth and isolation of the margin
- Cementation of the definitive crown or bridge
Simone
Simone has all her own beautiful teeth, except for two that were badly broken in an accident. They are right in the front so Simone is extremely relieved now they are restored and no-one can tell which ones they are!
She sent these photos to show how happy she is she can smile without embarrassment.
