Inlays and onlays are dental restorations for teeth which have developed decay.
Inlays are smaller and usually go into the crevices between the cusps (pointed parts) on the biting surface of a tooth. Onlays are larger and can cover multiple cusps, the entire biting surface, and even the sides of a tooth.
Inlays and onlays are stronger than fillings, longer lasting, and used for larger areas of decay. Inlays and onlays are smaller than dental crowns, more inexpensive, and require less tooth enamel removal.
Inlays and onlays are often applied to the teeth in the back of your mouth because these teeth have larger biting surfaces, several cusps, and are more vulnerable to tooth decay.
After the decay is drilled away from the tooth, your dentist will use a dental putty to make a mold of your tooth. This mold is used to make the inlay or onlay. After the restoration is created, your dentist will check its fit and bond it to the tooth.
Inlays and onlays are made of stronger materials than dental fillings since they are created outside of the mouth. They are so durable, that some inlays and onlays can last up to 30 years.