What are dental onlays and inlays? The use of inlays and onlays is considered a more conservative approach for the treatment of certain dental problems. Sometimes rather than cover a tooth completely with a crown, and inlay or onlay can be prepared to cover only a portion of the tooth that needs repair. As such, they are an excellent both for cosmetic dentistry and for repairing damaged teeth. Inlays and onlays are referred to as such because that is how they work -- they are prepared outside the mouth and then laid in or laid on the area of the tooth that needs to be covered. Inlays and onlays are therefore fabricated in a dental lab before they are bonded to the tooth. The dentist will make a mold of the tooth creating a template, so to speak, from which the inlay or onlay will be fabricated. These means it takes at least two dental visits to complete the inlay or onlay process.