FDI Notation
Pronunciation: F-D-I no-TAY-shun
Also written as: FDI — Fédération Dentaire Internationale Notation
A two-digit tooth numbering system in which the first digit identifies the quadrant and the second identifies the tooth within that quadrant, used as the international standard for tooth labeling in clinical and research documents.
Full Definition
Under the FDI (ISO 3950) system, quadrants are numbered 1–4 for permanent teeth and 5–8 for primary teeth, proceeding clockwise from the upper right. The tooth within each quadrant is numbered 1 (central incisor) to 8 (third molar). Thus, tooth '21' is the upper-left central incisor. Editors must ensure that FDI notation is applied consistently throughout an orthodontic document and is not mixed with the Universal Numbering System or Palmer notation without a conversion note. A space is not placed between the two digits; '2 1' is incorrect—'21' is correct.
Usage
Usage note: Do not insert a space between the two digits (e.g., '21' not '2 1'). Do not mix notation systems within a single document. Expand FDI on first use in formal documents: 'FDI (Fédération Dentaire Internationale) notation'.
In Context
- "Using FDI notation, the impacted canine was recorded as tooth 23." — Orthodontic referral letter
- "The author mixed FDI and Palmer notations across tables; the editor standardized all references to FDI for the international journal." — Proofreading log