What is the difference between an inlay and regular filling?

Dental inlay. In dentistry, an inlay is an indirect restoration (filling) consisting of a solid substance (as gold or porcelain) fitted to a cavity in a tooth and cemented into place.An onlay is the same as an inlay, except that it extends to replace a cusp. Crowns are onlays which completely cover all surfaces of a tooth.
Procedure and Cost. An inlay is an indirect procedure while a filling is a direct one. The filling is also less expensive. Ask your dentist about your individual treatment options as well as what your dentist charges for each treatment.
Strength. Lab made inlays, onlays, 3/4 crowns are all stronger than chairside direct fillings, bondings, and especially gold inlays or zirconia inlays, they are very resilient and tend to hold up longer. They also cost more, but they are worth it.
How it's made... Once the tooth is prepared for a filling, an inlay or filling (either white or silver) is used to cover the hole. The main difference is that an inlay is made outside while a filling is made inside your mouth. Because an inlay is made outside the mouth, we can use different materials such as gold or porcelain that would otherwise not be possible to make inside your mouth.