[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/) › Lower 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/) # Lower left first premolar The lower left first premolar (tooth 34) 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_34&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). ## What it does Crushes and tears food. ## Key points - Its buccal cusp is large and pointed while the lingual cusp is small and barely reaches the bite, so it looks like a step between canine and premolar - Its single root sometimes splits or hides 2 or more canals deep down, which makes it a difficult tooth for root canal treatment - Like the other first premolars, a frequent choice for extraction to relieve crowding in orthodontics ## 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](https://durgical.com/en/anatomy/inferior-alveolar-nerve/) (V3) ## Relations **In front** The [lower left canine](https://durgical.com/en/anatomy/lower-left-canine/) **Behind** The [lower left second premolar](https://durgical.com/en/anatomy/lower-left-second-premolar/) **Above** The [upper left canine](https://durgical.com/en/anatomy/upper-left-canine/) and the [upper left first premolar](https://durgical.com/en/anatomy/upper-left-first-premolar/) **Below** [Mental foramen](https://durgical.com/en/anatomy/mental-foramen/), behind and below its root tip, where the mental nerve and vessels leave the [mandible](https://durgical.com/en/anatomy/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](https://durgical.com/en/anatomy/lower-left-first-molar/) (FDI 74). ## Related conditions - [Dental caries](https://durgical.com/en/conditions/dental-caries/) ## 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. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/lower-left-first-premolar/) Educational information, not medical advice. For any symptom, see a health professional. ## Related - [Mandible](https://durgical.com/en/anatomy/mandible/) 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/lower-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/lower-left-first-premolar/