Digestive system · Head and neck
Upper left second premolar !
The upper left second premolar (tooth 25) 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 maxilla (gomphosis held by the periodontal ligament); bites against the opposing teeth
- Landmarks
- FDI 25, upper left second premolar: 1 root; two cusps of about equal height; erupts at about 10–12 years; nerve: middle superior alveolar nerve (V2)
Relations
- In front
- The upper left first premolar
- Behind
- The upper left first molar
- Above
- The maxillary sinus floor, often only thin bone away
- Below
- Meets the lower left second premolar and the lower left first molar
How to find it
The fifth tooth from the midline on the upper left, just ahead of the first molar, with a cheek-side and a palate-side cusp of similar height.
On imaging
On a panoramic or periapical film its root tip often overlaps the sinus floor; in children the panoramic shows the germ cradled between the primary molar's roots.
Clinical notes
- Supplied by the middle superior alveolar nerve, which many people lack; buccal infiltration still numbs it through the upper dental plexus
- Infection at its apex can spread into the maxillary sinus and cause odontogenic sinusitis, typically one-sided and foul-smelling
- Notches at the gum line from wear and flexing (non-carious cervical lesions) often affect upper premolars like this one
Development
Replaces the primary upper left second molar (FDI 65); if the premolar is missing from birth, that primary molar can stay in the mouth into adult life.
Related conditions
Test yourself
Think of the answer, then tap the question to see it.
Of the premolars, which one's root most often lies against the maxillary sinus floor?
The upper second premolar, such as the upper left second premolar.
What sinus complication can infection at the apex of the upper left second premolar cause?
Odontogenic sinusitis, typically one-sided and foul-smelling.
What happens if the upper left second premolar is missing from birth?
The primary upper left second molar (FDI 65) can stay in the mouth into adult life.
In a child, where does a panoramic film show the germ of the upper left second premolar?
Between the roots of the primary second molar it will replace.
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.
