[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) › Upper left first premolar [Digestive system](https://durgical.com/en/anatomy/system/digestive-system/) · [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) # Upper left first premolar The upper left first premolar (tooth 24) is the tooth just behind the canine; it helps crush and grind food. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=head_neck&select=teeth_24&side=r) Opens in the Durgical app, no sign-up needed. ## What it is A transition tooth between the canine and the molars, with two cusps (cheek side and [tongue](https://durgical.com/en/anatomy/tongue/) side); the upper first premolar often has two roots. ## What it does Crushes and tears food. ## Key points - Usually the only premolar with 2 root canals; a missed canal is a classic cause of failed root canal treatment in this tooth - Its buccal cusp is clearly taller than the palatal one, so from the side it looks like a small canine - Often removed in pairs with the other first premolars to gain space in orthodontic treatment ## Key facts **Joints with** Alveolar socket of the [maxilla](https://durgical.com/en/anatomy/maxilla/) (gomphosis held by the periodontal ligament); bites against the opposing teeth **Landmarks** FDI 24, upper left first premolar: usually 2 roots (buccal and palatal); two cusps; often removed for orthodontic space; erupts at about 10–11 years; nerve: middle superior alveolar nerve (V2) ## Relations **In front** The [upper left canine](https://durgical.com/en/anatomy/upper-left-canine/) **Behind** The [upper left second premolar](https://durgical.com/en/anatomy/upper-left-second-premolar/) **Lateral** Cheek and [buccinator](https://durgical.com/en/anatomy/bucinator/) across the buccal vestibule **Below** Meets the [lower left first premolar](https://durgical.com/en/anatomy/lower-left-first-premolar/) and the [lower left second premolar](https://durgical.com/en/anatomy/lower-left-second-premolar/) ## How to find it Behind the upper left canine, the fourth tooth from the midline; seen from the cheek side its tall buccal cusp looks like a small canine. ## On imaging Bitewing radiographs catch decay hidden at its contacts with the canine and the second premolar; an angled periapical splits the two roots so neither canal is missed. ## Common problems - Often the tooth removed to make space in orthodontic treatment. ## Clinical notes - Supplied by the middle superior alveolar nerve, an inconstant branch; when it is absent, fibres from the anterior and posterior superior alveolar nerves take over, and buccal infiltration still numbs the tooth - When the [maxillary sinus](https://durgical.com/en/anatomy/maxillary-sinus/) extends far forward its floor can reach above these roots, so the ache of sinusitis may be felt in this tooth ## Anatomical variants - Many have a single root holding 2 canals instead of 2 separate roots; rarely there are 3 roots (two buccal, one palatal) ## Development Replaces the primary [upper left first molar](https://durgical.com/en/anatomy/upper-left-first-molar/) (FDI 64). The primary molars are wider than the premolars that follow them, and the spare room (leeway space) helps the permanent teeth line up. ## Related conditions - [Dental caries](https://durgical.com/en/conditions/dental-caries/) ## Test yourself Think of the answer, then tap the question to see it. ## Which premolar usually has 2 root canals? The upper first premolar, such as the upper left first premolar; a missed canal is a classic cause of failed root canal treatment. ## Why may the ache of sinusitis be felt in the upper left first premolar? When the maxillary sinus extends far forward, its floor can reach above this tooth's roots. ## What is leeway space? The spare room left because the primary molars are wider than the premolars that replace them, such as the upper left first premolar; it helps the permanent teeth line up. ## Which radiograph best shows hidden decay between the upper left first premolar and its neighbours? The bitewing radiograph. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/upper-left-first-premolar/) Educational information, not medical advice. For any symptom, see a health professional. ## Related - [Maxillae](https://durgical.com/en/anatomy/maxilla/) Sources: [Anatomy, Head and Neck, Teeth](https://www.ncbi.nlm.nih.gov/books/NBK557543/); [Anatomy, Permanent Dentition](https://www.ncbi.nlm.nih.gov/books/NBK570590/); [Anatomy, Head and Neck, Tooth Eruption](https://www.ncbi.nlm.nih.gov/books/NBK549878/); [Anatomy, Head and Neck: Alveolar Nerve](https://www.ncbi.nlm.nih.gov/books/NBK546712/); [23.3 The Mouth, Pharynx, and Esophagus](https://openstax.org/books/anatomy-and-physiology-2e/pages/23-3-the-mouth-pharynx-and-esophagus) (OpenStax (Rice University), 2022) · adapted, [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/upper-left-first-premolar/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/upper-left-first-premolar/