Onlays and inlays can both be utilized to conservatively repair teeth that have large defective fillings or have been damaged by decay or trauma. Onlays and inlays are an ideal alternative to crowns (caps) because less tooth structure is removed in the preparation process. 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.
Reasons for onlay or inlay restorations: