Crowns are basically a covering, or ”cap” which overlays the entire portion of the tooth that is visible above the gum line. It mimics the shape and size of the original tooth and is cemented on permanently. Crowns are done to restore the size, shape and strength of a tooth.
Crowns can be made of many different materials; however, recently we mostly use a very hard substance called zirconia, or zirconium dioxide, which has exceptional longevity and durability. Zirconia used in dentistry is the white crystalline oxide form. This is not to be confused with the cubic crystalline form, or cubic zirconia, that is used as an economical form of diamond jewelry. Zirconia is also chemically unreactive and biocompatible. For these reasons, as well as its ability to look like a natural tooth, zirconia has become the material of choice for crowns. Other materials like gold, porcelain fused to metal, and resin have been used to make crowns but none of these materials exceed all the positive assets of zirconia.
In order for a crown to fit correctly, the natural tooth needs to be reduced all around by approximately 2 mm. This makes room to accommodate the thickness of the crown. If a crown were to be placed on top of the tooth without reduction, it would be too tall and throw off one’s “bite.” During the preparation procedure, any decay present will be removed as well as old fillings. A fine margin is shaped around the gum line of the tooth, which is like a shelf that the crown will sit upon when cemented.
Most of the time crowns are needed due to breakdown of tooth structure. There are many ways this happens, but the most common reason is fracture due to a cavity or decay. The decay process weakens the tooth and it will ultimately break.
Large fillings can fracture under normal chewing forces. When there is not enough tooth structure to support a filling, the next step is to protect the tooth with a full coverage crown. Large amalgam (silver) fillings will sometimes cause “cracked tooth syndrome” where the natural tooth supporting the filling cracks and causes pain when chewing. Most of the time we can see theses cracks clinically, but sometimes they are under the filling and cannot be detected with an x-ray. The crown will cover the tooth and hold it together to prevent more cracking.
Crowns are used to cover and protect misshapen or severely worn down teeth. In these cases, crowns are used to restore function. Crowns can be fabricated to restore the tooth to the correct shape and contour to enhance normal chewing function.
Crowns are necessary almost always on a tooth that has had a root canal. Teeth are essentially hollowed out for root canal therapy and will be very weak until the crown is cemented.
Dental implants are restored using crowns as well after a natural tooth has been lost. The implant, which is a titanium post, is placed in the jawbone; it replaces the root of the original tooth. Then an abutment is screwed into the implant post and a crown is placed upon that.
Obviously crowns are a large part of restoring a healthy, functioning mouth!
There are many reasons why the doctors at Broad Ripple Martin Dentistry will diagnose the necessity of a crown in your individual case.