[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 right first molar [Digestive system](https://durgical.com/en/anatomy/system/digestive-system/) · [Head and neck](https://durgical.com/en/anatomy/region/head-and-neck/) # Lower right first molar The lower right first molar (tooth 46) is a large back tooth that comes in around age 6; it does much of the chewing. [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=head_neck&select=teeth_46&side=r) Opens in the Durgical app, no sign-up needed. ## What it is A large back tooth with a broad chewing surface of five cusps (three on the cheek side, two on the [tongue](https://durgical.com/en/anatomy/tongue/) side) and two roots. ## What it does Grinds food before swallowing. ## Key points - 5 cusps (3 buccal, 2 lingual) and usually 3 canals: 2 in the mesial root and 1, sometimes 2, in the distal root - An inferior alveolar nerve block numbs the tooth, but the buccal gum needs the buccal nerve, and accessory fibres (for example from the [mylohyoid](https://durgical.com/en/anatomy/mylohyoid-muscle/) nerve) can explain a failed block - In Angle Class I occlusion the mesiobuccal cusp of the upper right first molar sits in this tooth's buccal groove ## Key facts **Joints with** Alveolar socket of the [mandible](https://durgical.com/en/anatomy/mandible/) (gomphosis held by the periodontal ligament); bites against the opposing teeth **Landmarks** FDI 46, lower right first molar: 2 roots (mesial and distal); first permanent tooth to erupt; key to the bite (occlusion); erupts at about 6–7 years; nerve: inferior alveolar nerve (V3) ## Relations **In front** The [lower right second premolar](https://durgical.com/en/anatomy/lower-right-second-premolar/) **Behind** The [lower right second molar](https://durgical.com/en/anatomy/lower-right-second-molar/) **Above** Meets the [upper right second premolar](https://durgical.com/en/anatomy/upper-right-second-premolar/) and the [upper right first molar](https://durgical.com/en/anatomy/upper-right-first-molar/) **Below** Inferior alveolar canal with the [inferior alveolar nerve](https://durgical.com/en/anatomy/inferior-alveolar-nerve/), artery and vein ## How to find it The five-cusped tooth sixth from the midline on the lower right; it comes in at about 6 years behind the primary second molar, often unnoticed because no tooth falls out. ## On imaging Bitewing radiographs reveal decay hidden in its contacts and fissures; periapicals show its two roots, the furcation and the apices against the canal below. ## Common problems - Tooth decay (caries) often starts in the grooves of the chewing surface. ## Clinical notes - It replaces no tooth and is often mistaken for a baby tooth, so decay in its deep grooves can go unnoticed in children - When it is lost early, the second molar tips forward into the gap and the opposing upper teeth drift down - Molar-incisor hypomineralisation often affects this tooth: soft, discoloured enamel that crumbles and decays early ## Anatomical variants - A third root on the distolingual side (radix entomolaris) is a recognised variant, seen more often in people of East Asian ancestry ## Development No primary predecessor: it grows from a backward extension of the dental lamina and begins to calcify around birth, so disturbances in the first months of life can show in its enamel. ## Memory aid Lower eruption order: 6-1-2-3-4-5-7-8 (the first molar and the central incisor often come in together). Compare the upper arch, where the canine comes after the premolars. ## Related conditions - [Dental caries](https://durgical.com/en/conditions/dental-caries/) - [Periodontitis](https://durgical.com/en/conditions/periodontitis/) ## Test yourself Think of the answer, then tap the question to see it. ## Where does the mesiobuccal cusp of the upper right first molar sit on the lower right first molar in Angle Class I occlusion? In the buccal groove of the lower right first molar. ## What happens when the lower right first molar is lost early? The second molar tips forward into the gap and the opposing upper teeth drift down. ## Why can decay of the lower right first molar go unnoticed in children? It replaces no tooth and is often mistaken for a baby tooth, so decay in its deep grooves is missed. ## Which permanent molar is the usual target of fissure sealants in children? The first permanent molar, such as the lower right first molar, soon after it erupts at about 6 years. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/lower-right-first-molar/) 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-right-first-molar/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/lower-right-first-molar/