Inlays and onlays are a type of dental restoration that is bigger than a filling but smaller than a dental crown. Inlays usually go between the pointed parts of a tooth (cusps) located on the chewing surface while onlays can cover one or more of these cusps and the sides of the tooth.
Because inlays and onlays are used for bigger areas of decay than fillings, they are often placed in the teeth at the back of the mouth because these molars have a larger chewing surface, several cusps, and are more susceptible to decay. Large fillings can weaken a tooth, but inlays and onlays are stronger and can last up to 30 years. They are easier to clean and more inexpensive than crowns.
Your dentist will apply an inlay or onlay by first removing decay and any old fillings from the tooth. After cleaning and preparation is completed, they will make an impression of the tooth using dental putty. This impression is sent to a dental lab for inlay/onlay creation, so you will wear a temporary restoration while you wait. Once the inlay/onlay is complete, your dentist will test its fit and then bond it to your tooth.