Each tooth is represented by a 2-digit number. The upper and lower arch each contains 8 permanent teeth numbered from the midline toward the back from 1 to 8 for the adult dentition.
Each arch is subdivided in 2 quadrants or semi-arches, a right and left one, indicated by the first digit. The upper right quadrant is #1, and the left one is #2. The lower arch includes quadrants #3 (at the bottom left) and #4 (at the bottom right).
Teeth in quadrant #1 are numbered starting with “1” followed by the number identifying the tooth (1 to 8). Teeth in quadrant #2 start with “2” and so on for each quadrant.