Inlays and onlays are often referred to as partial crowns. They use the existing tooth as a foundation and fit into or onto the tooth. This is done to strengthen the tooth, restore its shape, and prevent further damage. An inlay is done when there is no damage to the cusps of the tooth and the inlay can be placed right on the tooth. An onlay is used when the damage is a little more extensive.
Inlays and onlays may be made from porcelain or gold. Some consideration must be given to the choice between porcelain and gold, as these material have different advantages. Generally speaking, porcelain offers the best esthetic result if the treatment area is within the "smile zone", while gold offers the most durability and predictability. Porcelain is very resistant to wear, but may cause wear on opposing teeth if a patient chenches or grinds his or her teeth. Gold is very gentle to opposing tooth surfaces and requires removal of less tooth structure than does porcelain. Gold, however, does not have the natural tooth color.
When an inlay or onlay is planned, the decayed area of the tooth is first removed during the procedure. A base may then be placed to give an ideal prepared shape. A mold of the tooth is then taken and sent to a dental lab. The lab technician creates a restoration made from porcelain or gold. The restoration takes about three weeks to make, so a temporary inlay or onlay will be placed on the tooth for that time. During your next visit the inlay or onlay will be placed into your mouth and set with cement. Your tooth will feel natural. A porcelain inlay or onlay will also look completely natural. A gold inlay or onlay can often be designed to be nearly invisible in your smile.
The cost of an inlay or onlay is generally higher than that of composite or amalgam due to the number and length of the visits required and the laboratory costs. Inlays and onlays are conservative ways to preserve tooth structure on some teeth that would otherwise need full-coverage crowns.