FDI/ISO System (permanent teeth) (English)

The maxillary and mandibular dental arches are separated in the midline into quadrants (2 maxillary and 2 mandibular quadrants). The FDI (Fédération Dentaire Internationale) or ISO (International Organization for Standardization) system is the most commonly employed means of tooth notation across the world. It uses a number combination where the first number corresponds to the quadrant in which the tooth is located (upper right quadrant = 1, upper left quadrant = 2, lower left quadrant = 3, lower right quadrant = 4) while the second number (1-8) corresponds to the tooth position working mesial to distal. For example, the maxillary right first molar receives the number ‘16’, since it’s located in quadrant 1 and is the 6th tooth working mesial to distal.