Replacements for decayed or lost teeth have been produced for millennia. TheEtruscans made skillfully designed false teeth out of ivory and bone, securedby gold bridgework, as early as 700 b.c. Unfortunately, thislevel of sophistication for false teeth was not regained until the 1800s. During medieval times, the practice of dentistry was largely confined to tooth extraction; replacement was seldom considered. Gaps between teeth were expected, even among the rich and powerful. Queen Elizabeth I (1533-1603) filled theholes in her mouth with cloth to improve her appearance in public. When false teeth were installed, they were hand-carved and tied in place with silk threads. If not enough natural teeth remained, anchoring false ones was difficult. People who wore full sets of dentures had to remove them when they wantedto eat. Upper and lower plates fit poorly and were held together with steel springs; disconcertingly, the set of teeth could spring suddenly out of the wearer's mouth. Even George Washington (1732-1799) suffered terribly from toothloss and ill-fitting dentures. The major obstacles to progress were findingsuitable materials for false teeth, making accurate measurements of a patient's mouth, and getting the teeth to stay in place. These problems began to besolved during the 1700s. Since antiquity, the most common material for falseteeth was animal bone or ivory, especially from elephants or hippopotami. Human teeth were also used, pulled from the dead or sold by poor people from their own mouths. These kinds of false teeth soon rotted, turning brown and rancid. Rich people preferred teeth of silver, gold, mother of pearl, or agate. In 1774 the French pharmacist Duchateau enlisted the help of the prominent dentist Dubois de Chemant to design hard-baked, rot-proof porcelain dentures. DeChemant patented his improved version of these "Mineral Paste Teeth" in 1789and took them with him when he emigrated to England shortly afterward. The single porcelain tooth held in place by an imbedded platinum pin was inventedin 1808 by the Italian dentist Giuseppangelo Fonzi. Inspired by his dislike of handling dead people's teeth, Claudius Ash of London, England, invented animproved porcelain tooth around 1837. Porcelain teeth came to the United States in 1817 via the French dentist A. A. Planteau. The famous artist Charles Peale (1741-1847) began baking mineral teeth in Philadelphia, Pennsylvania, in1822. Commercial manufacture of porcelain teeth in the United States was begun, also in Philadelphia, around 1825 by Samuel Stockton. In 1844 Stockton'snephew founded the S. S. White Company, which greatly improved the design ofartificial teeth and marketed them on a large scale. Fit and comfort, too, gradually improved. The German Philip Pfaff (1715-1767) introduced plaster of paris impressions of the patient's mouth in 1756. Daniel Evans of Philadelphiaalso devised a method of accurate mouth measurement in 1836. The real breakthrough came with Charles Goodyear's discovery of vulcanized rubber in 1839. This cheap, easy-to-work material could be molded to fit the mouth and made agood base to hold false teeth. Well-mounted dentures could now be made cheaply. The timing was fortuitous. Horace Wells (1815-1848) had just introduced painless tooth extraction using nitrous oxide. The number of people having teeth removed skyrocketed, creating a great demand for good, affordable dentures, which Goodyear's invention made possible. After 1870, another cheap base, celluloid, was tried in place of rubber, but it too had drawbacks.
Today dentures are primarily made of plastic or ceramic. However, research continues into new and better materials to make dentures longer lasting and more resistant to stain. One such material is cobalt chromium, which is a hard metal that does not rust or change shape. A more recent development in dentistry is the dental implant. Dental implants are constructed from biocompatiblematerials, such as titanium, which are not recognized by the body's immune system as foreign. Endosteal implant are placed into the bone to replace the root portion of a tooth. A subperiosteal implant--used when there is not enoughbone left--fits in a framework fashion over the remaining bone. These implants are then used to support a natural looking artificial tooth, which is usually attached with a dental adhesive.