Inlays and onlays can be made of porcelain or gold. These pieces are bonded to the damaged area of the tooth. An inlay is used inside the cusp tips of the tooth, whereas an onlay extends over one or more of the cusps of the tooth.
    Traditionally, gold has been the material of choice for inlays and onlays. In recent years, with advanced technology, ceramic (or porcelain) has become the material of choice because of the natural appearance, strength and ability to bond directly to enamel.

Traditional fillings can reduce the strength of a natural tooth by up to 50 percent. As an alternative, inlays and onlays, which are bonded directly to the tooth using high-strength resins or cements, can actually increase the strength of a tooth by up to 103 percent.