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Topic

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Inferior third molar tooth

The inferior third molar, commonly known as the mandibular wisdom tooth, is the most posterior tooth in the mandibular dental arch. It typically erupts between the ages of 17 and 25 years, although eruption patterns vary. The tooth may be fully erupted, partially erupted, or impacted due to limited jaw space. Anatomically, it consists of a crown with occlusal, buccal, and lingual surfaces, one to three roots, and a pulp chamber containing neurovascular bundles. Its position and angulation in the mandible are highly variable, making it clinically significant for impaction, pericoronitis, caries, and surgical extraction planning.

Synonyms

  • Mandibular third molar

  • Wisdom tooth

  • Lower third molar

Function

  • Plays a minor role in mastication, mainly grinding food

  • Helps maintain posterior occlusion if fully erupted

  • Provides anchorage and support for the mandibular dental arch

  • Can act as a landmark for mandibular surgery and radiographic assessment

MRI Appearance
T1-weighted images:

  • Tooth enamel appears very low signal (dark) due to its dense mineral content

  • Dentin shows intermediate signal, while the pulp chamber is hyperintense, allowing visualization of neurovascular contents

  • Surrounding alveolar bone appears intermediate to low signal, with marrow fat hyperintense

  • Pathology such as periapical cysts or abscesses may appear hyperintense in the marrow or soft tissues

T2-weighted images:

  • Enamel remains hypointense, dentin intermediate

  • Pulp chamber is bright (hyperintense) due to water content

  • Periapical lesions, inflammation, or cysts are highlighted as hyperintense areas

STIR (Short Tau Inversion Recovery):

  • Fat suppression makes marrow hypointense, improving detection of edema, inflammation, or early infection

  • The pulp remains hyperintense, while pathological changes appear bright against suppressed fat

CT Appearance

  • The inferior third molar is highly radiodense (white) due to enamel and dentin

  • Pulp chamber appears radiolucent (dark)

  • Surrounding alveolar bone is intermediate density, with cortical bone clearly visible

  • CT is ideal for assessing impaction, root morphology, proximity to the inferior alveolar canal, fractures, or cystic lesions

  • Air in the oral cavity or soft tissue spaces appears hypodense (black), providing contrast for tooth and bone structures

MRI images

Inferior third molar tooth mri axial image -img-00000-00000

MRI images

Inferior third molar tooth mri sag image -img-00000-00000