Inlays and Onlays are lab-made restorations that are placed on teeth when the cavity or lost tooth structure is too large to be restored by a simple filling. The process of making an inlay is very similar to a crown. After the inlay is prepared, it is cemented or bonded to the tooth.
There are different materials that inlays are made of including gold, porcelain, and composite resins. Porcelain and composite inlays and onlays are cosmetic alternatives to fillings and are very strong compared to regular white fillings. Gold inlays and onlays are also suitable alternatives, but their appearance makes them less popular.
Your dentist will explain when an inlay or onlay is a treatment option for you. In general, inlays and onlays can replace most back teeth fillings and are sometimes cosmetically preferred over conventional fillings. They are also more conservative than crowns.
As far as cost is concerned, because the process of making an inlay or onlay is similar to a crown, its cost is also comparable. However, when considering the longevity of inlays and onlays, they can end up costing less than traditional fillings.