FDI World Dental Federation notation
FDI World Dental Federation notation (also called FDI notation or ISO 3950 notation) is the world's most commonly used dental notation (tooth numbering system). It is designated by the International Organization for Standardization as standard ISO 3950 "Dentistry — Designation system for teeth and areas of the oral cavity".
Source: Wikipedia — FDI World Dental Federation notation (CC BY-SA 4.0)