Once the decay has penetrated the surface of the enamel and a cavity has formed, the emphasis shifts from prevention to restoration. The tooth cannot repair itself; instead, your dentist must correct the damage. If the damage extends into the dentin (but has not yet reached the pulp) and the tooth is stable, repair usually means cleaning out the area and filling the cavity. How Your Dentist Fills a Cavity After numbing the area, your dentist will clean away the decayed enamel using a high-speed rotary drill, an air-abrasive device, or a laser system. He or she may also use a slower drill or manual scooping tool to remove damaged dentin. Once the decayed portion is removed, your dentist will cut the hole into a shape that enables the filling to adhere securely and gives the rest of the tooth the most support. The next steps depend on the size of the hole to be filled and the material to be used. In some cases, the dentist will coat the inside of the hole with a lining material that prevents tooth sensitivity, seals against leakage, and helps the filling material adhere. This step is often taken for large or deep cavities. When tooth-colored fillings (composites) are used, the dentist must etch the interior of the prepared cavity with acid to ensure that the filling material adheres to the enamel. Silver amalgam restorations are generally completed in one visit with no other preparatory steps. Other types may take more than one visit to complete. Inlays (which fit into the tooth) and onlays (which fill the tooth and cover part of the biting surface) must be specially made to match the size and shape of the area being filled. These restorations, which are usually reserved for larger cavities, may take two or three visits to complete