An onlay may be required to repair larger cavities in the chewing surfaces of back teeth, increasing their strength by covering the cusps while maintaining their appearance. They are an excellent alternative to crowns as they are more conservative in nature requiring much less tooth removal in comparison to a crown. Onlays are made in a laboratory and can be fabricated in gold or ceramic.

Compared to a crown, an onlay is a less aggressive restoration when one can be performed, as less tooth structure needs to be removed in order to place the onlay.  For this reason, an onlay is the preferred restoration when possible.

The number of appointments required are the same and the costs are similar.