Dentistry schools use three kinds of dental charts to instruct students: the Universal Numbering System, the Palmer Notation System, and the International System. The most widely used system in the US is the Universal Numbering System.
Different dental notation systems have different ways of assigning a number or letter to every tooth.
The Universal Numbering System starts counting from the upper-right molar and moves clockwise until it ends with the lower-right third molar. Teeth in the permanent dentition are assigned numbers from 1 to 32, while teeth in the primary dentition are indicated by letters from A to T.
The International Numbering System employs a two-digit method of notation, with the first number indicating the quadrant a tooth is located in, and the second indicating its position within that quadrant. The quadrants in permanent dentition are numbered 1 to 4, starting from the upper-right corner and moving clockwise to the lower left. Quadrants in primary dentition are numbered 5 to 8 and are also counted from the upper-right to lower-left. Individual numbering always starts from the central incisors and moves out towards the molars.
The Palmer Notation System also orders teeth by quadrants, but uses symbols (?? ?? represent quadrant 1 to 4) to indicate the quadrant in which the tooth is found. Adult teeth are individually numbered from 1 to 8, while teeth in the primary dentition are indicated by letters from A to E. Individual numbering starts out from the central incisors and moves out towards the molars. So for instance, the upper-right molar in the permanent dentition is indicated as ?8, while the upper-right molar in the primary dentition is indicated as ?E.