Dental inlays treat decay or damage within the cusps (top projections of a tooth), while dental onlays treat decay or damage that includes one or more of the cusps. Tooth-colored fillings, inlays, and onlays not only look more natural, they also feel more natural than their metal counterparts.
Traditional fillings can reduce the strength of a natural tooth by up to 50 percent. As an alternative, inlays and onlays, which are bonded directly onto the tooth using special high-strength resins, can actually increase the strength of a tooth by up to 75 percent. As a result, they can last for a significantly longer period of time. In some cases, where the damage to the tooth is not extensive enough to merit an entire crown, onlays can provide a very good alternative.