Digestive system · Head and neck
Lower left first premolar !
The lower left first premolar (tooth 34) is the tooth just behind the canine; it helps crush and grind food.
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What it is
A transition tooth between the canine and the molars, with two cusps (cheek side and tongue side).
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 34, lower left first premolar: 1 root; two cusps; often removed for orthodontic space; erupts at about 10–12 years; nerve: inferior alveolar nerve (V3)
Relations
- In front
- The lower left canine
- Behind
- The lower left second premolar
- Above
- The upper left canine and the upper left first premolar
- Below
- Mental foramen, behind and below its root tip, where the mental nerve and vessels leave the mandible
How to find it
Fourth tooth from the midline on the lower left, right behind the canine; its big pointed buccal cusp and tiny lingual cusp make it look canine-like.
On imaging
A periapical shows its root and the dark mental foramen nearby; when the canal seems to vanish partway down, it usually splits, and an angled view or CBCT helps.
Common problems
- Often the tooth removed to make space in orthodontic treatment.
Clinical notes
- Inferior alveolar nerve (V3): numbed by an inferior alveolar nerve block, or by a mental (incisive) block at the mental foramen
- Surgery or implants near its apex can injure the mental nerve, leaving the lower lip and chin numb on that side
Anatomical variants
- Dens evaginatus: a small extra tubercle on the biting surface, mostly on lower premolars and more frequent in East Asian ancestry; if it breaks it can expose the pulp
Development
Replaces the primary lower left first molar (FDI 74).
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
How do the cusps of the lower left first premolar look?
A large, pointed buccal cusp and a small lingual cusp that barely reaches the bite, a step between canine and premolar.
Which nerve can be injured by surgery or implants near the apex of the lower left first premolar, and with what result?
The mental nerve: the lower lip and chin go numb on that side.
Why is the lower left first premolar a difficult tooth for root canal treatment?
Its single root sometimes splits or hides 2 or more canals deep down.
What is dens evaginatus of the lower left first premolar, and why does it matter?
A small extra tubercle on the biting surface; it can break off and expose the pulp.
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.
