Both inlays and onlays are considered “indirect” fillings, meaning that they are fabricated outside the mouth (usually by a dental laboratory) and then bonded to the tooth by the dentist. This is in contrast to a “direct” filling, which is applied directly to the cavity by the dentist in one office visit. An indirect filling is considered an “inlay” when it fits within the little points or “cusps” of a back (premolar or molar) tooth. It is an “onlay” if it covers one or more of these cusps. Either way, the procedure for placing an inlay or onlay is the same.