In the dentistry world, inlays and onlays are terms used to refer to indirect restorations that are perfect to repair teeth with a mild to moderate levels of decay. They are considered indirect because the restorations are made outside of the mouth as a single solid piece, perfectly sized to fit the shape of the decayed portion of your teeth. They are bigger than fillings but smaller than a crown. More specifically dental inlays are used to treat teeth that have decay within their indented top surfaces. It lies within the bumps (cusps) on the chewing surface of your tooth. Whereas, dental onlays replace one or more decayed cusps. Additionally, they may also be used to repair chipped or injured teeth, if the damage is not severed enough to require a dental crown.
Inlays and onlays are usually made from porcelain or composite resin. In some cases an inlay or onlay can be made from gold. Also, since, they are made from tooth-coloured materials that are a great solution for those looking to replace their metal filings or for a more natural looking appearance.