Digestive system · Head and neck
Lower right second molar !
The lower right second molar (tooth 47) is the back tooth behind the first molar that comes in around age 12; it grinds food.
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What it is
A large back tooth behind the first molar, with two roots.
What it does
Grinds food before swallowing.
Key facts
- Joints with
- Alveolar socket of the mandible (gomphosis held by the periodontal ligament); bites against the opposing teeth
- Landmarks
- FDI 47, lower right second molar: 2 roots; erupts behind the first molar around age 12; erupts at about 11–13 years; nerve: inferior alveolar nerve (V3)
Relations
- In front
- The lower right first molar
- Behind
- The lower right third molar; when that tooth is impacted it often leans against this tooth's back surface
- Above
- Meets the upper right first molar and the upper right second molar
- Medial
- Tongue and floor of the mouth, with the lingual nerve running a little higher and further back
How to find it
The seventh tooth from the midline on the lower right, with four almost equal cusps; it comes in at about 12 years behind the first molar.
On imaging
On a panoramic film its roots sit nearer the inferior alveolar canal than the first molar's; a C-shaped canal shows as fused roots and is confirmed by CBCT.
Common problems
- Tooth decay (caries) in the grooves of the chewing surface.
Clinical notes
- Supplied by the inferior alveolar nerve (V3), so it needs an inferior alveolar nerve block; the thick outer bone of the mandible here stops infiltration from working well
- Its root tips lie below the mylohyoid line, so infection spreads to the submandibular space
Anatomical variants
- C-shaped root canal, where the roots fuse into a horseshoe-shaped root, is a known variant of this tooth, more frequent in East Asian populations
Development
No primary predecessor: it develops from the dental lamina behind the first molar and erupts at about 12 years.
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
Why does the lower right second molar need an inferior alveolar nerve block rather than infiltration?
The thick outer bone of the mandible here stops infiltration from working well.
Which root canal variant is typical of the lower right second molar?
The C-shaped canal, where the roots fuse into a horseshoe-shaped root; more frequent in East Asian populations.
Where does infection from the roots of the lower right second molar spread?
To the submandibular space, because its root tips lie below the mylohyoid line.
On a panoramic film, how do the roots of the lower right second molar relate to the inferior alveolar canal?
They lie closer to the canal than the first molar's roots.
Educational information, not medical advice. For any symptom, see a health professional.
Related
Sources: Anatomy, Head and Neck, Teeth; Anatomy, Permanent Dentition; Anatomy, Head and Neck, Tooth Eruption; Anatomy, Head and Neck: Alveolar Nerve; 23.3 The Mouth, Pharynx, and Esophagus (OpenStax (Rice University), 2022) · adapted, CC BY 4.0.
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Representative model, for educational purposes only.
