Inlays are indirect fillings pre-made in a dental lab and must be permanently cemented by a dentist. Fillings are different from indirect fillings in that they are soft to begin with and set in the mouth. As opposed to an onlay (the other type of indirect filling), which sits on the tooth and builds up its shape, inlays fit into the space left after a cavity or old filling has been removed.

Inlays are generally made in tooth-coloured porcelain but are also made in gold or composite materials. Inlays are far more durable than fillings, don't require much of the actual tooth structure to be removed in order to place them, and actually increase the strength of the tooth by up to 75%, preventing further decay. Since inlays are made outside the mouth, they are usually very strong and last up to thirty years. Inlays are aesthetically pleasing as they can be made to match the tooth color and as such, don't draw attention.

Applying an inlay is a two visit dental procedure. During the first visit, the tooth decay or old filling material will be removed. A mold of the tooth and adjacent teeth is taken and sent to a dental lab. In the meantime, a temporary filling will be applied to protect the tooth. During the second appointment, the dentist will cement the inlay in place, making any necessary adjustments to ensure a comfortable bite.