← All explanationsTooth fusion

Why does a tooth look like two joined teeth?

Tooth fusion occurs when two developing teeth unite. An unusually broad or divided crown may be a clue. Root and canal anatomy can vary; the outside appearance alone cannot establish the diagnosis.

For training & practice ↓

Teaching model of two developmentally joined incisors with a broad double crown and two roots. — One possible form of tooth fusion. Root and canal anatomy vary; the image cannot establish a diagnosis.

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Two developing teeth

The union develops while the teeth form. It is not the later gluing together of two finished teeth.

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Notice the groove

A groove at the junction can be difficult to clean. Cavity risk and possible protection are assessed.

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The whole dentition

Tooth count, successors and internal anatomy are considered together. Not every broad crown needs alteration or separation.

Read the full explanation

Two developing teeth
The union develops while the teeth form. It is not the later gluing together of two finished teeth.
Notice the groove
A groove at the junction can be difficult to clean. Cavity risk and possible protection are assessed.
The whole dentition
Tooth count, successors and internal anatomy are considered together. Not every broad crown needs alteration or separation.

Notes on the teaching images

One possible form of tooth fusion. Root and canal anatomy vary; the image cannot establish a diagnosis.

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Watch the short explanation ↓

At a glance

Origin?

Two developing teeth unite.

Cleaning concern?

A possible groove at the junction.

Automatically treat?

No, according to function and findings.

Knowledge in motion

Explained in 36 seconds.

Three steps. No audio.
Each scene can also be selected manually.

Silent educational film with German on-screen text and simplified teaching images. Not a patient case or a promised treatment outcome. The full English explanation is available as text.

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Often confused

Two developing teeth or one?

Fusion joins two developing teeth. Gemination starts from one. Tooth count is a clue, not an infallible test.

Quick answers

Is the tooth count always reduced?

The count is often unusual, but fusion with an extra tooth may leave an apparently normal count.

Is this the same as gemination?

No. Gemination involves attempted division of one developing tooth. Distinguishing them clinically can be difficult.

What can I do when cleaning?

Clean the groove carefully but gently and ask which tools are appropriate. Do not split or grind it yourself.

At the practice

For a personal discussion

Editorially suggested question to discuss with Dr Niusha Barahmand Pour:

How can the groove be protected, and what internal anatomy matters?

A broad crown or deep groove can be assessed for cleanability and developmental variation.

Have tooth shape assessedAppointment selection at Doctolib

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Learning layer for training & practiceUnderstand terminology and deepen knowledge

Double tooth: A descriptive term for certain broad or divided tooth shapes.
Developmental groove: A groove related to crown development.
Canal anatomy: The arrangement of internal tooth spaces.

Make the distinction

Fusion joins two developing teeth. Gemination starts from one. Tooth count is a clue, not an infallible test.

Knowledge questionWhy is counting alone insufficient?

For learning, not for assessing personal symptoms. Your answer is not stored or sent.

An extra tooth may be involved.
Every double tooth is definitely gemination.
Roots never matter.

View answer

An extra tooth may be involved.

Shape, number and internal anatomy must be considered together.

Sources and context

Editorial research: 2026-11-06. General information, not an individual diagnosis or treatment recommendation. Teaching illustrations are simplified and do not depict a patient case.