What does “FDI tooth numbering” mean?
FDI notation identifies teeth using two digits. The first specifies the upper or lower jaw, right or left side, and primary or permanent dentition. The second gives the tooth's position within that quadrant, counted from the midline.
The first digit identifies the quadrant
For permanent teeth, the patient's upper right is 1, upper left 2, lower left 3, and lower right 4. Primary teeth use 5, 6, 7, and 8 in the same order. When facing a dental chart, its right and left may appear reversed relative to your own.
The second digit counts from the midline
Within each quadrant, permanent teeth are numbered 1–8 from the central incisor, and primary teeth 1–5. For example, 11 identifies the upper right permanent central incisor, and 51 the upper right primary central incisor. The two digits have separate roles rather than forming a simple running sequence.
Transferring records between clinics
Countries and clinics may use different numbering systems. When sharing previous records or a treatment plan, checking the tooth's name, jaw, and side alongside its number can reduce confusion. Do not infer the treatment site from an unexplained number alone.
Frequently Asked Questions
Are 11 and 51 the same tooth?
Both refer to the upper right central-incisor position, but in FDI notation 11 is permanent and 51 is primary. They are not two ways of labelling the same tooth.
Can I compare a foreign clinic's tooth numbers directly?
First check that the systems match. Universal and FDI assign numbers differently, so directly equating the same number can identify the wrong tooth.
Questions about tooth numbering
Learn what the term means and how it relates to your dental condition.
- Sufficient understanding
Does the record specify FDI notation?
Explanation and evidenceA number that appears to have two digits does not by itself establish the system. Check the notation used in the record.
American Dental Association · Universal Tooth Designation System - Sufficient understanding
Have you confirmed the patient's right and left sides and whether the tooth is primary or permanent?
Explanation and evidenceMatch the code to the actual tooth location when confirming the treatment site.
American Dental Association · Universal Tooth Designation System
Further reading and references
References
- International Organization for Standardization · ISO 3950:2016iso.org (opens in a new tab)
- Australian Dental Association · The Australian Schedule of Dental Services and Glossaryada.org.au (opens in a new tab)
- American Dental Association · Universal Tooth Designation Systemada.org (opens in a new tab)
