Digestive system · Head and neck
Lower left second premolar !
The lower left second premolar (tooth 35) is the tooth between the first premolar and the first molar; it helps crush and grind food.
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What it is
A transition tooth with two cusps and one root, just in front of the molars.
What it does
Crushes and tears food.
Key facts
- Joints with
- Alveolar socket of the mandible (gomphosis held by the periodontal ligament); bites against the opposing teeth
- Landmarks
- FDI 35, lower left second premolar: 1 root; two or three cusps; lies near the mental foramen; erupts at about 11–12 years; nerve: inferior alveolar nerve (V3)
Relations
- In front
- The lower left first premolar
- Behind
- The lower left first molar
- Above
- The upper left first premolar and the upper left second premolar
- Below
- Mental foramen, usually just below the root tip, with the inferior alveolar canal running below toward it
How to find it
Fifth tooth from the midline on the lower left, directly in front of the first molar; most have one buccal and two small lingual cusps.
On imaging
In a child, a panoramic film shows its germ between the roots of the primary second molar, or its absence. In adults a periapical with a change of beam angle tells the mental foramen from an apical lesion.
Clinical notes
- Inferior alveolar nerve (V3); the mental nerve, leaving the foramen beside its root, supplies the lip and chin and is at risk with implants, flaps or a difficult extraction
- Early loss of the primary second molar lets the first permanent molar tip forward and close the space, so this premolar may be left without room to erupt
Anatomical variants
- The lingual side has one cusp (two-cusp type) or two (three-cusp type with a Y-shaped groove, the more common form)
Development
Replaces the primary lower left second molar (FDI 75), a large primary tooth shaped like a small first molar.
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
What can mimic a lesion at the apex of the lower left second premolar on a radiograph?
The mental foramen, most often found below or just in front of its root tip.
What happens when the lower left second premolar is missing from birth?
The primary lower left second molar (FDI 75) may stay into adult life; this premolar is one of the teeth most often missing after the third molars.
Which nerve is at risk with implants, flaps or a difficult extraction of the lower left second premolar?
The mental nerve, leaving the mental foramen beside its root; it supplies the lip and chin.
Which radiograph shows whether the lower left second premolar is missing from birth in a child?
A panoramic film, which shows each premolar germ between the roots of the primary molar above it.
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.
