Inlays and onlays, also known as indirect fillings, are used to replace a small, moderate, or even significant amount of tooth structure lost to decay. These restorations serve as well-fit, durable, and aesthetically-pleasing solutions. An inlay or onlay is ideal if there is too much damage for a filling, but not enough to require the use of a dental crown.
An indirect filling is considered an inlay when the restoration fits within the occlusal, or bite surface, of the tooth (the center). An indirect filling is considered an onlay when it extends beyond one or more cusps of the tooth.
These days, most inlays and onlays are fabricated using a ceramic material like porcelain. Porcelain can be colored and textured to match the appearance of your natural enamel. In other words, a ceramic inlay or onlay will be virtually indistinguishable from the rest of your tooth. In the past, these restorations were also fabricated using gold, although this material has fallen out of favor for cosmetic reasons.