FDI two-digit notation
The FDI two-digit notation is the internationally standard shorthand for identifying individual teeth. Each tooth is assigned a two-digit code: the first digit identifies the quadrant (1–4 for permanent teeth, 5–8 for deciduous teeth) and the second identifies the tooth within that quadrant.
Abkürzung der französischen Fédération Dentaire Internationale; „Schema“ von griechisch schéma „Gestalt, Form“
Zweistellenschema, ISO 3950, WHO-Zahnschema, internationales Zahnschema
FDI two-digit notation
How does the system work?
The dentition is divided into four quadrants. In the permanent dentition, the upper right quadrant is numbered 1, upper left 2, lower left 3, and lower right 4 — from the patient's perspective. In the deciduous dentition the quadrants run from 5 to 8. The second digit counts from the midline backwards from 1 to 8. Tooth 11 is therefore the upper right central incisor, 36 is the lower left first molar, 48 is the lower right wisdom tooth, 55 is the upper right second deciduous molar. The number is spoken digit by digit, so “one one” not “eleven”. Positions 1 and 2 are incisors, 3 is the canine, 4 and 5 are premolars, 6 to 8 are molars; in the deciduous dentition the count ends at 5.
Where does it come from and what is it used for?
The two-digit system, developed by the Berlin academic Joachim Viohl, was adopted by the Fédération Dentaire Internationale at its 1970 annual meeting in Bucharest. Today it is standardised as ISO 3950 and is also called the WHO notation. In Germany, dental charts, treatment and cost plans, and billing under BEMA and GOZ all use it. Older notations such as the Zsigmondy cross or the American Universal Numbering System with numbers 1 to 32 are still encountered in textbooks and in records from abroad.
Why this matters for graduates from EU countries
Bulgaria, Romania, Hungary, Croatia, and the Baltic states also use FDI for documentation, so the transition is straightforward. The situation is different with records from the USA. Those who translate records or document prior treatment should always state the notation system, otherwise mix-ups occur. The tooth number is combined with surface designations such as mesial or approximal, producing the concise notations used in dental charts and treatment plans. Practice management software in Germany works exclusively with FDI; conversion is only needed for imported external records.
Typical mistake
Right and left refer to the patient, not the observer. Those who confuse this document on the wrong tooth.
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