An onlay is used to rebuild a tooth that has damage to one or more cusps. This treatment helps to restore optimal shape and function while saving as much of the natural tooth as possible. This is important because natural tooth structure is always better than an artificial material, which in the case of an onlay can be ceramic, composite, or a combination of both. At your first appointment, your doctor will take an impression or mold to help make a temporary onlay for your tooth. Next, the tooth is prepared to make room for the onlay. Your doctor will take another impression of the minimally prepared tooth and put in a temporary onlay while the final restoration is being constructed by an expert lab technician. At a subsequent appointment, your doctor will remove the temporary onlay and replace it with the final restoration. Since this restoration has been expertly crafted outside of the mouth, the final restoration will generally last longer than a large filling. Once completed, your tooth is restored to optimal shape and function, and much of the natural tooth structure is saved.