The term "crown" is used to describe the portion of your tooth that extends above the gumline - in other words, the portion of the tooth that can be seen in a healthy mouth. It is also used more colloquially to describe the dental procedure of having a prosthetic "crown" placed over a decayed, chipped, cracked, or otherwise damaged tooth.
With this dental procedure code, the prosthetic crown is constructed predominately of base metal, but only covers 3/4 of the tooth's overall surface. A crown of this nature is designated as such because less than 25% of its composition is of the noble metals gold, platinum, palladium, and silver, and its predominant makeup is of chromium and nickel. Noble metals are known to interact with human tissue well, and hold up to corrosion and oxidation better than other metals. The higher the percentage of noble metals, the less likely a crown is to corrode or oxidize, as is the case with a 3/4 Cast High Noble Metal Crown and a 3/4 Cast Noble Metal Crown, which contain a higher amount of noble metals.
In this procedure, the entire biting surface of the tooth is covered with base metal, along with a portion of the tooth that rests alongside the tongue. For cosmetic reasons, the healthy portion of the tooth that faces your cheek (and is visible when smiling), is left intact. At times, the top ridge of the crown that covers the biting surface may be seen in particularly wide smiles. Because a 3/4 crown only covers a portion of the tooth, less of the tooth needs to be removed, resulting in greater aesthetics while still benefiting from the strength of the metals used.
To prepare for this type of crown, a dentist will first remove any decayed or weakened areas of the tooth, and reduce its overall shape to accommodate the crown. A mold of your bite will then be made, so the custom crown can be fabricated off-site at a dental lab. If desired, a temporary crown can be fitted until the custom crown is completed.