Designating teeth: the advantages of the FDI's two-digit system.

For more than 130 years, several systems for designating and encoding teeth have been in use. Starting with the oldest one, which was proposed by Zsigmondy and Palmer, the most important methods are briefly described. Because none of these early systems complies with the requirements set by the Fédération Dentaire Internationale, the organization introduced its own two-digit system in 1970. Although this system has not gained worldwide recognition yet, it has many advantages over the other methods and should be universally adopted.