# Tooth 31: Lower Right Second Molar

> In the Universal Numbering System, tooth 31 is the lower right second molar (mandibular right second molar). Its FDI (ISO 3950) designation is 47 and its Palmer designation is 7 in the lower right quadrant. It is a molar in the lower arch with typically 2 roots.

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Last verified: 2026-07-08

Neutral tooth-designation reference only; not clinical, diagnostic, or treatment advice. Root counts describe typical permanent-tooth morphology and vary between individuals.

## Direct answer

- Which tooth is number 31? In the Universal Numbering System, tooth 31 is the lower right second molar (mandibular right second molar). Its FDI (ISO 3950) designation is 47 and its Palmer designation is 7 in the lower right quadrant. It is a molar in the lower arch with typically 2 roots.
- Universal number: 31
- FDI / ISO 3950 designation: 47
- Palmer designation: 7 LR
- Plain-language name: Lower Right Second Molar
- Anatomical name: Mandibular Right Second Molar
- Quadrant: Lower Right
- Arch and side: lower, right
- Type: molar
- Typical roots: 2

## Conversion table

| System | Designation |
| --- | --- |
| Universal Numbering System | 31 |
| FDI / ISO 3950 | 47 |
| Palmer notation | 7 LR |
| Tooth name | Lower Right Second Molar |

## Search terms

- which tooth is number 31?
- tooth 31
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- lower right second molar
- mandibular right second molar
- fdi 47
- palmer 7
- lower right tooth 7
- lower right molar

## Sources

- `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/>

## Related

- [Full tooth numbering chart](https://dentovio.com/tools/tooth-numbering-chart/index.html.md)
- [FDI to Universal converter](https://dentovio.com/tools/fdi-to-universal-converter/index.html.md)
- [Palmer notation converter](https://dentovio.com/tools/palmer-notation-converter/index.html.md)
- [Previous tooth: Tooth 30: Lower Right First Molar](https://dentovio.com/tools/tooth-numbering-chart/tooth-30/index.html.md)
- [Next tooth: Tooth 32: Lower Right Third Molar](https://dentovio.com/tools/tooth-numbering-chart/tooth-32/index.html.md)