An onlay restoration is a custom made restoration. An onlay is sometimes also referred to as a partial crown.
Onlays can be utilized to conservatively repair teeth that have large defective fillings or have been damaged by decay or trauma. Onlays are an ideal alternative to crowns (caps) because less tooth structure is removed in the preparation of onlays. Onlays are essentially identical to inlays with the exception that one or more of the chewing cusps have also been affected and need to be included in the restoration.
As with most dental restorations, onlays are not always permanent and may someday require replacement.
Reasons for onlay restorations: