Differences Between Maxillary and Mandibular First Molars

Sep 10, 2024

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Maxillary First Molar vs. Mandibular First Molar

General Characteristics

  • Position: Both are the sixth tooth from the midline in their respective arches.
  • Tooth Notation Numbers: Differ based on their arch placement.
  • Eruption Age: Both erupt around 6-7 years, with the mandibular molar generally erupting earlier.

Development

  • Formation: Develop from 5 lobes.
    • Maxillary: Fifth cusp lobe.
    • Mandibular: Distal lobe.
  • Cusps: Both have 5 cusps.
    • Maxillary has 4 functional, 1 non-functional.
    • Mandibular has all 5 functional.

Root Structure

  • Maxillary Molar: 3 roots.
  • Mandibular Molar: 2 roots with developmental depressions giving an I-beam appearance.

Dimensions

  • Crown Length: Equal in both molars.
  • Mesio-Distal Dimension: Larger in the mandibular molar.
  • Bucco-Lingual Dimension: Larger in the maxillary molar.
  • Root Length: Longer in the mandibular molar.

Morphology

Buccal Aspect

  • Maxillary: 2 cusps visible (mesio-buccal and disto-buccal).
  • Mandibular: 3 cusps visible (mesio-buccal, disto-buccal, and distal).
  • Grooves:
    • Maxillary has 1 buccal developmental groove.
    • Mandibular has 2 buccal grooves.

Lingual Aspect

  • Maxillary: 3 cusps visible, including the cusp of Carabelli.
  • Mandibular: 2 cusps visible.
  • Root Visibility: All roots visible in maxillary, both visible in mandibular.

Mesial Aspect

  • Maxillary Crown Shape: Trapezoidal.
  • Mandibular Crown Shape: Rhomboidal.
  • Cusps Visibility:
    • Maxillary: 3 cusps visible.
    • Mandibular: 2 cusps visible.
  • Cervical Line Tilt: Present in mandibular but not in maxillary.

Distal Aspect

  • Cusps Visibility:
    • Maxillary: 2 cusps visible.
    • Mandibular: 2 cusps, more of occlusal surface visible due to lower distal marginal ridge.

Occlusal Aspect

  • Maxillary Shape: Rhomboidal.
  • Mandibular Shape: Hexagonal.
  • Diameters:
    • Maxillary: Larger bucco-lingual.
    • Mandibular: Larger mesio-distal.
  • Primary & Secondary Cusps:
    • Maxillary has 3 primary and 2 secondary.
    • Mandibular has 4 primary and 1 secondary.
  • Oblique Ridge: Present in maxillary only.

Grooves and Fossae

  • Grooves:
    • Maxillary has 6 grooves, mandibular has 4.
    • Maxillary has a distal oblique groove and transverse groove of oblique ridge.
  • Fossae:
    • Maxillary: Central (triangular) and distal (linear).
    • Mandibular: One circular central fossa.

These notes outline the differences and characteristics of the maxillary first molar and mandibular first molar in terms of development, structure, morphology, and grooves.