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# Lower left central incisor

The lower left central incisor (tooth 31) is a small flat front tooth beside the midline that cuts food.

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## What it is

A front tooth with a thin, straight cutting edge and one root.

## What it does

Bites into and cuts food; shapes some speech sounds (f, v, th).

## Key points

- Smallest permanent tooth; its root is flattened side to side and often holds 2 canals (labial and lingual), easy to miss on a front-on radiograph
- The only lower tooth that meets a single upper tooth: the upper central incisor
- It often erupts behind (lingual to) a primary incisor that has not yet fallen out, giving a short-lived double row of teeth

## Key facts

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

**Landmarks**
FDI 31, lower left central incisor: 1 root; chisel-shaped crown for cutting; erupts at about 6–7 years; nerve: [inferior alveolar nerve](https://durgical.com/en/anatomy/inferior-alveolar-nerve/) (V3)

## Relations

**Medial**
The [lower right central incisor](https://durgical.com/en/anatomy/lower-right-central-incisor/), across the midline

**Lateral**
The [lower left lateral incisor](https://durgical.com/en/anatomy/lower-left-lateral-incisor/)

**Above**
The [upper left central incisor](https://durgical.com/en/anatomy/upper-left-central-incisor/), whose palatal surface overlaps it in front

**Behind**
Tip and underside of the [tongue](https://durgical.com/en/anatomy/tongue/); the [submandibular gland](https://durgical.com/en/anatomy/submandibular-gland/) ducts open on the floor of the mouth just behind it

## How to find it

Just left of the lower midline (the patient's left), the narrowest tooth in the mouth; pull down the lower lip to see it, or look from behind with a mirror for tartar on its tongue side.

## On imaging

A periapical shifted sideways (angled) separates the labial and lingual canals that overlap on a straight view. On a panoramic film this narrow front region is often blurred, so periapicals are preferred.

## Common problems

- Chipped or broken front teeth after falls or blows.

## Clinical notes

- Supplied by the incisive branch of the inferior alveolar nerve (V3), with fibres crossing from the other side at the midline; the labial bone is thin here, so infiltration works, unlike for the lower molars
- Thin labial bone and gum make this area prone to gum recession, more so with crowding or a strong lower labial frenum
- Periodontitis in teenagers and young adults may concentrate on the incisors and first molars (molar-incisor pattern), and the thin bone here shows the loss early

## Development

Replaces the primary lower left central incisor (FDI 71); the permanent germ develops lingual to the primary root.

## Related conditions

- [Periodontitis](https://durgical.com/en/conditions/periodontitis/)

## Test yourself

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

## Which is the smallest permanent tooth, and what root canal feature is easy to miss?

The lower central incisor, such as the lower left central incisor; its flattened root often holds 2 canals (labial and lingual).

## Which is the only lower tooth that meets a single upper tooth?

The lower central incisor, such as the lower left central incisor: it meets only the upper central incisor.

## Why does infiltration numb the lower left central incisor, unlike the lower molars?

Its labial bone is thin; it is supplied by the incisive branch of the inferior alveolar nerve (V3), with fibres crossing from the other side.

## Why is the lower left central incisor better seen on a periapical than on a panoramic film?

The narrow front of the panoramic image layer often blurs this region; an angled periapical also separates its two canals.

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

## Related

- [Mandible](https://durgical.com/en/anatomy/mandible/)

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/lower-left-central-incisor/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/lower-left-central-incisor/