TEETH, ARTIFICIAL. In the beginning of the restora tive art in dentistry, artificial substitutes were human teeth, teeth of cattle and sheep, teeth carved from the tusks of the ele phant, and from the tooth of the hippopotamus. The first re corded substitute other than animal substances was a paste made of white wax, gum elemi and the powder of white mastic, of coral, and of pearl. It was originated by the Frenchman, Guille meau, in 1598. In 1728 Fauchard, also a Frenchman, used jewel lers' enamel and gold plate in developing a technique for making artificial teeth. Porcelain teeth were introduced into America about 1817, reputedly by Plantou (1774-1837). Silica, kaolin and feldspar are the three basic materials used in the manufacture of porcelain teeth. Silica is used as a vehicle for holding the form of the tooth ; it is of selected high quality and has an exceptionally high fusing point. Kaolin adds density and strength and forms the body material of the tooth. Felspar is the flux, which com bines the silica and kaolin, thereby forming a porcelain that is the finest in texture, translucency and quality, with a high degree of strength, yet developed in the ceramic arts. Colour is supplied through the use of the oxides of titanium, platinum, cobalt, iron, gold and tin. These materials, known as colouring frits, are incor porated with the basic ingredients to produce the tints desired. Artificial teeth are first carved in plaster or other suitable ma terial to a size approximately one-fifth larger than the desired finished product. This allows for the shrinkage in the porcelain
during the fusion process. Moulds of hard metallic substance are made from the enlarged plaster teeth and the porcelain is packed in them in the form of a paste. After hardening to a bisque form, the teeth are removed from the moulds, placed in a furnace, and fused at a temperature varying from 1,700 to 2,500° F. Crowns, facings and vulcanite teeth are the types required to meet indi vidual needs. Porcelain crowns are used to replace the crowns of natural teeth when their roots are in place. The porcelain crown is attached to the natural root by means of a post that is fitted and cemented to place. Facings are of the veneer type and are used to restore the loss of one or more teeth by bridge work. Vulcanite teeth are generally used when partial or full sets of den tures are required. These teeth are attached to a base and made to fit over the various individual forms of the gums. Materials used for bases are hard rubber, gold, platinum or bakelite. The typal classification of selecting artificial teeth is the one now in current use. There are three basic typal forms of faces, square, tapering and ovoid, and the teeth harmonize with these types. (M. M. H.)