Inlays are restorations that are usually fabricated from porcelain, ceramic, or gold. These days most inlays are made in a tooth-coloured porcelain or ceramic material so that the restoration blends in with the natural tooth.
An inlay restoration is contained within the cusp tips of the tooth.
Inlays are used to repair moderately damaged back teeth and are extremely strong to withstand the grinding and pressures of these teeth.
Inlays are fabricated in a laboratory then glued into place with a special glue that creates a strong bond between the tooth structure and inlay.
Onlays are a more extensive repair of a damaged tooth that covers the cusps of the tooth.
An onlay is much stronger than any other type of filling material and actually increases the strength of the tooth.
Onlays are also fabricated from porcelain or ceramic, and used to repair back teeth.