Any of the various systems developed for designating teeth in a chart system including numbers, letters, or symbols. They are not uniformly accepted. Widely used are the two-digit system of Federation Dentaire Internationale (FDI system) and the American system, which numbers the permanent teeth consecutively from the upper right third molar as #1 through the maxillary teeth to #16, and then to the left mandibular third molar as #17 and through the mandibular teeth to the right third molar as #32.