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# Upper right third molar

The upper right third molar (tooth 18) is the wisdom tooth, last at the back; it often lacks room to come in and stays stuck (impacted).

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## What it is

The wisdom tooth: the last molar, usually coming in between the ages of 17 and 25.

## What it does

Grinds food when it erupts fully; often it does not.

## Key points

- When impacted it usually sits upright or tilted backward (distoangular) in the maxillary tuberosity
- During removal it can be pushed into the maxillary sinus or back into the infratemporal fossa, and the maxillary tuberosity can fracture
- Usually erupts between about 17 and 21 years, if at all; third molars are also the teeth most often missing from birth

## Key facts

**Joints with**
Alveolar socket of the [maxilla](https://durgical.com/en/anatomy/maxilla/) (gomphosis held by the periodontal ligament); bites against the opposing teeth

**Landmarks**
FDI 18, upper right third molar (wisdom tooth): roots often fused or variable; often impacted or missing; erupts at about 17–25 years; nerve: posterior superior alveolar nerve (V2); roots near the floor of the maxillary sinus

## Relations

**In front**
The [upper right second molar](https://durgical.com/en/anatomy/upper-right-second-molar/)

**Behind**
Maxillary tuberosity; behind it, the pterygoid plates and the infratemporal fossa

**Above**
Floor of the [maxillary sinus](https://durgical.com/en/anatomy/maxillary-sinus/), often very close

**Below**
In a normal bite it meets only one tooth, the [lower right third molar](https://durgical.com/en/anatomy/lower-right-third-molar/)

## How to find it

The last tooth on the upper right, eighth from the midline, against the maxillary tuberosity; often absent, unerupted or only partly visible.

## On imaging

A panoramic film is the first study: it shows its depth in the tuberosity and how close it lies to the sinus floor; CBCT helps when it sits high or inside the sinus wall.

## Common problems

- Impacted wisdom tooth: stuck under the gum or against the second molar, with pain, swelling or infection (pericoronitis).

## Clinical notes

- Posterior superior alveolar nerve, entering the tuberosity just above and behind it; the pterygoid venous plexus and branches of the [maxillary artery](https://durgical.com/en/anatomy/maxillary-artery/) lie close behind
- When it erupts tilted toward the cheek it can rub or be bitten against the buccal mucosa
- Hard to reach with a toothbrush, so it decays easily and can trap plaque against the back of the second molar

## Anatomical variants

- Its crown is the most variable of the upper teeth: often 3 cusps or a small peg, with roots that are frequently fused into one
- A small extra molar can sit behind it (distomolar) or on its cheek side (paramolar)

## Development

Among the last tooth germs to form: calcification starts at about 9–10 years and the roots finish in the early twenties, which is why third-molar stage is used to estimate age.

## Memory aid

FDI 18 = quadrant 1, tooth 8. In the US Universal system it is #1: the count starts here and runs across the upper arch to #16.

## Test yourself

Think of the answer, then tap the question to see it.

## How is an impacted upper right third molar usually positioned?

Upright or tilted backward (distoangular) in the maxillary tuberosity.

## Where can the upper right third molar be displaced during removal?

Into the maxillary sinus or back into the infratemporal fossa; the maxillary tuberosity can also fracture.

## What are the FDI and US Universal numbers of the upper right third molar?

FDI 18 (quadrant 1, tooth 8) and Universal #1, where the count begins.

## At what age does the upper right third molar usually erupt?

Between about 17 and 21 years, if it erupts at all.

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Educational information, not medical advice. For any symptom, see a health professional.

## Related

- [Maxillae](https://durgical.com/en/anatomy/maxilla/)

Sources: [Anatomy, Head and Neck, Teeth](https://www.ncbi.nlm.nih.gov/books/NBK557543/); [Anatomy, Permanent Dentition](https://www.ncbi.nlm.nih.gov/books/NBK570590/); [Anatomy, Head and Neck, Tooth Eruption](https://www.ncbi.nlm.nih.gov/books/NBK549878/); [Anatomy, Head and Neck: Alveolar Nerve](https://www.ncbi.nlm.nih.gov/books/NBK546712/); [23.3 The Mouth, Pharynx, and Esophagus](https://openstax.org/books/anatomy-and-physiology-2e/pages/23-3-the-mouth-pharynx-and-esophagus) (OpenStax (Rice University), 2022) · adapted, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/upper-right-third-molar/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/upper-right-third-molar/