Porcelain inlays and onlays are very aesthetic alternatives to composite fillings. They have a high degree of strength, and as such, are excellent for restoring weakened back teeth. Inlays and onlays protect and restore large portions of decayed, heavily restored tooth, or teeth under very heavy load (i.e. back teeth). Unlike crowns, they only cover a portion of the tooth and are therefore more conservative on the amount of tooth preparation required.