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Permanent Maxillary Left First Molar

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Dental Anatomy Dental Glossary

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Permanent Maxillary Left First Molar

The permanent maxillary left first molar is the upper-left first permanent molar, designated tooth #14 in the Universal Numbering System (UNS) and UL6 in FDI notation. It typically erupts between ages 6 and 7, commonly called the six-year molar, and plays a foundational role in establishing posterior occlusion and overall bite development.

Anatomy and Structure

The crown features four primary cusps — mesiobuccal, distobuccal, mesiolingual, and distolingual — arranged around a central fossa. A fifth accessory cusp, the Cusp of Carabelli, is frequently present on the mesiolingual cusp and serves as a distinctive anatomical landmark used in identification and anthropological study. Thick enamel covers the broad occlusal surface to withstand heavy masticatory forces, though the deep developmental pits and fissures make this tooth particularly prone to carious lesions without preventive intervention.

The root complex consists of three distinct roots:

  • Mesiobuccal root — often curved and notorious for harboring a second mesiobuccal canal, commonly called MB2
  • Distobuccal root — shorter and more conical in cross-section
  • Palatal root — the longest and widest of the three, oriented toward the palate

The periodontal ligament suspends each root within the alveolar socket, and the interradicular bone separating the roots defines the furcation area — a region of primary concern during periodontal evaluation and treatment planning.

Clinical Significance

As the first permanent tooth to erupt, the permanent maxillary left first molar establishes the posterior occlusal plane and directly shapes bite relationships as the remaining permanent dentition develops. Its roots sit in close proximity to the maxillary sinus floor, particularly the palatal and mesiobuccal roots, creating risk for sinus communication during extraction and complicating implant site preparation. The mesiobuccal root frequently contains two separate root canals, making endodontic treatment more technically demanding and accounting for a disproportionate share of missed canals in clinical outcomes research.

Key clinical considerations include:

  • Occlusal caries initiating in deep developmental grooves
  • Pit-and-fissure sealant placement as a primary preventive measure
  • Furcation involvement in moderate to advanced periodontal disease
  • MB2 canal detection and negotiation during root canal therapy
  • Potential maxillary sinus communication during surgical extraction or implant planning

Given its early eruption and central role in posterior function, preserving the permanent maxillary left first molar through timely preventive and restorative care represents one of the highest-value interventions in long-term oral health management.