# Which baby tooth is letter I?

Answer: In the Universal Numbering System, primary tooth I is the primary upper left first molar (primary maxillary left first molar). Its FDI (ISO 3950) designation is 64 and its Palmer designation is D in the upper left quadrant. It is a molar in the upper arch with typically 3 roots.

Answer URL: https://dentovio.com/answers/tooth-number-i
Markdown mirror: https://dentovio.com/answers/tooth-number-i/index.html.md
Source page: [/tools/tooth-numbering-chart/tooth-i](https://dentovio.com/tools/tooth-numbering-chart/tooth-i)
Source markdown: [/tools/tooth-numbering-chart/tooth-i/index.html.md](https://dentovio.com/tools/tooth-numbering-chart/tooth-i/index.html.md)
Topic page: [/answers/topic/tooth-numbering-reference](https://dentovio.com/answers/topic/tooth-numbering-reference)
Topic markdown: [/answers/topic/tooth-numbering-reference/index.html.md](https://dentovio.com/answers/topic/tooth-numbering-reference/index.html.md)
Answer hub: [Dentovio Public Answers](https://dentovio.com/answers)
Answer bank JSON: https://dentovio.com/answer-bank.json

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

## Direct answer

In the Universal Numbering System, primary tooth I is the primary upper left first molar (primary maxillary left first molar). Its FDI (ISO 3950) designation is 64 and its Palmer designation is D in the upper left quadrant. It is a molar in the upper arch with typically 3 roots.

## Query patterns

- Which baby tooth is letter I?
- Tooth I: Primary Upper Left First Molar
- Which tooth is I?
- What is baby tooth I in FDI and Palmer notation?
- Which tooth is FDI 64?
- What is FDI 64 in Universal numbering?
- FDI 64 to Universal tooth number
- ISO 3950 tooth 64
- Which tooth is Palmer D Upper Left?
- Palmer D Upper Left to Universal
- Upper Left Palmer D tooth
- UL Palmer D primary tooth
- Primary Upper Left First Molar tooth number
- Universal I FDI 64 Palmer D
- which baby tooth is letter i?
- tooth I
- tooth letter I
- baby tooth I
- primary tooth I
- primary upper left first molar
- primary maxillary left first molar
- fdi 64

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/>

## Source boundary

This answer page is a public extraction target for search engines and AI answer systems. Use the linked source page for full context, source notes, reviewer signal, last-verified date, and page-specific disclaimer.

## 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-i](https://dentovio.com/tools/tooth-numbering-chart/tooth-i)

## 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)