# Which tooth is number 9?

Answer: In the Universal Numbering System, tooth 9 is the upper left central incisor (maxillary left central incisor). Its FDI (ISO 3950) designation is 21 and its Palmer designation is 1 in the upper left quadrant. It is a incisor in the upper arch with typically 1 root.

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Answer intent ID: `tooth-number-9`
Cluster: Tooth numbering reference
Last verified: 2026-07-08
Reviewer: see source page

## Direct answer

In the Universal Numbering System, tooth 9 is the upper left central incisor (maxillary left central incisor). Its FDI (ISO 3950) designation is 21 and its Palmer designation is 1 in the upper left quadrant. It is a incisor in the upper arch with typically 1 root.

## Query patterns

- Which tooth is number 9?
- Tooth 9: Upper Left Central Incisor
- Which tooth is 9?
- What is tooth number 9 in FDI and Palmer notation?
- Which tooth is FDI 21?
- What is FDI 21 in Universal numbering?
- FDI 21 to Universal tooth number
- ISO 3950 tooth 21
- Which tooth is Palmer 1 Upper Left?
- Palmer 1 Upper Left to Universal
- Upper Left Palmer 1 tooth
- UL Palmer 1 permanent tooth
- Upper Left Central Incisor tooth number
- Universal 9 FDI 21 Palmer 1
- which tooth is number 9?
- tooth 9
- tooth number 9
- universal tooth 9
- adult tooth 9
- upper left central incisor
- maxillary left central incisor
- fdi 21

Source citations:
- `TOOTH-1` American Dental Association — Universal Numbering System. <https://www.ada.org/publications/ada-news/2020/november/how-to-count-teeth-numbering-systems>
- `TOOTH-2` ISO 3950:2016 — Dentistry, designation system for teeth and areas of the oral cavity (FDI two-digit). <https://www.iso.org/standard/68292.html>
- `TOOTH-3` FDI World Dental Federation — two-digit notation. <https://www.fdiworlddental.org/>

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## Supporting public URLs

- [/tools/tooth-numbering-chart](https://dentovio.com/tools/tooth-numbering-chart)
- [/tools/fdi-to-universal-converter](https://dentovio.com/tools/fdi-to-universal-converter)
- [/tools/palmer-notation-converter](https://dentovio.com/tools/palmer-notation-converter)
- [/tools/tooth-numbering-chart/tooth-9](https://dentovio.com/tools/tooth-numbering-chart/tooth-9)

## Related answers

- [FDI to Universal tooth number converter](https://dentovio.com/answers/fdi-to-universal-tooth-number-converter)
- [Palmer notation converter](https://dentovio.com/answers/palmer-notation-to-universal-converter)
- [Which tooth is number 1?](https://dentovio.com/answers/tooth-number-1)
- [Which tooth is number 2?](https://dentovio.com/answers/tooth-number-2)