A dental inlay or onlay is similar to a large dental filling, used to strengthen and repair decayed, cracked or fractured posterior teeth. The difference between inlays/onlays and fillings is that inlays and onlays are crafted in a dental laboratory, and custom fabricated to your tooth, akin to crowns. In a case where more than half of the biting surface of a tooth needs to be filled or repaired, an inlay or onlay is likely a better choice than a filling, being stronger and longer-lasting. These restorations are generally used as a more conservative option when more than a filling, but less than a crown, is needed.