The cast-metal inlay is an alternative to amalgam or composite when the higher strength of a casting alloy is needed or when the superior control of contours and contacts that the indirect procedure provides is desired. The cast-metal onlay is often an excellent alternative to a crown for teeth that have been greatly weakened by caries or by large, failing restorations but where the facial and lingual tooth surfaces are relatively unaffected by disease or injury. For such weakened teeth, the superior physical properties of a casting alloy are desirable to withstand the occlusal loads placed on the restoration; also the onlay can be designed to distribute occlusal loads over the tooth in a manner that decreases the chance of tooth fracture in the future. Sturdevant operative dentistry 7th Edition, Page No:e94