Human tooth development the cells of the IEE secrete an organic matrix against the dentin. This matrix immediately mineralizes and becomes the initial layer of the tooth's enamel. Outside the dentin are the newly formed ameloblasts in response to the formation of dentin, which are cells that continue the process of enamel formation; therefore, enamel formation moves outwards, adding new material to the outer surface of the developing tooth. Enamel formation is called amelogenesis and occurs in the crown stage (advanced bell stage) of tooth development. "Reciprocal induction" governs the relationship between the formation of dentin and enamel; dentin formation must always occur
Human tooth of the missing structure can be achieved with a variety of treatments. Restorations may be created from a variety of materials, including glass ionomer, amalgam, gold, porcelain, and composite. Small restorations placed inside a tooth are referred to as "intracoronal restorations". These restorations may be formed directly in the mouth or may be cast using the lost-wax technique, such as for some inlays and onlays. When larger portions of a tooth are lost, an "extracoronal restoration" may be fabricated, such as an artificial crown or a veneer, to restore the involved tooth. When a tooth is lost, dentures, bridges, or