Dental crowns are a fixed prosthesis that is manufactured by a dental lab that actually cements onto/over your natural tooth structure.
There are three types of dental crowns.
Ceramic. Ceramic crowns are an all-porcelain.
Porcelain that is fused to a metal substance such as gold or silver.
Full gold crown.
Why do teeth require dental crowns?
Typically a crown is required when a tooth is broken and a large portion of tooth structure is lost, such as a broken cusp or the filling broke out along with some of the tooth structure. In these cases, the tooth is so compromised that it:
1. Will not hold a large filling and
2. Because it's compromised, it needs something to cover the structure in order to protect what's left.
To receive a dental crown, the tooth is prepared and a mold is made. The crown will actually cement right over the top of the natural tooth structure. This is done to protect the remaining integrity of a tooth and to prolong its life and longevity.
What is the difference between a crown and a porcelain veneer?
Porcelain veneers actually are used generally in the front teeth and they're similar to a fake fingernail. A very thin piece of glass or porcelain is manufactured by the dental lab which will actually be cemented onto the front surface of the tooth. The tooth actually underneath the veneer is what gives the veneer some strength. The veneer in itself is not very strong at all, versus a crown, which actually derives its strength from the thickness of the porcelain or the metal underlying the crown.
Crowns generally will last most of a person's life if they're placed well and the person has good oral hygiene. Insurance companies allow crowns to be replaced every five years typically, some longer than that. Typically crowns will last several years. I've seen crowns last 20 or 30 years and so they can be good, long-term restoration when the tooth integrity is compromised.