In case of more extended tooth substance loss a direct filling is no longer the best choice. An extraorally fabricated restoration is preferable. These restorations are called onlays. They are fabricated from either composite resin or porcelain, depending on the particular situation. They are bonded to the remaining tooth with resin composite (white filling material).
They are highly esthetic restorations, as they are tooth colored and they recover to the utmost the original tooth anatomy and therefore they are practically invisible. Moreover they are a very conservative treatment, since no further tooth substance, other than the already missing, is removed.