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.
Once a tooth is removed there is no going back, so it is important to consider the alternatives to an extraction and what you intend to do with the space.
Your dentist will explain when an inlay or onlay is a viable treatment option for you. In general, inlays and onlays can replace most back teeth fillings and are sometimes cosmetically preferred over conventional fillings. At the same time, they are more conservative than crowns.