Onlays replace less of the healthy tooth than a full crown. Therefore, they are a more conservative treatment option, where the carving seeks to preserve the periphery of the tooth as much as possible, limiting it to the masticatory surface.
Dental inlays are a form of indirect restorations, meaning they are crafted outside the mouth using a plaster model of the damaged area, such as a cracked tooth, that requires reconstruction.
Composite resin: They are inlays made of the same resin material used in dental fillings, but they have greater shape stability, greater resistance, and better adaptation.
Onlays are considered the appropriate treatment in cases of tooth damage from decay or fracture where a filling would not suffice, but a crown would be a very aggressive option.