Dental Anatomy: Permanent Maxillary Molars

Permanent Maxillary Molars

• The largest and strongest teeth in the maxillary arch, with three roots: two buccal and one lingual (palatal).
• They erupt behind the deciduous molars and have a main function of grinding food and supporting the muscles of mastication and vertical dimension.

Maxillary First Molar

• The largest tooth in the maxillary arch.
• Principal identifying features:
  • Rhomboidal occlusal outline.
  • The presence of a fifth cusp (the cusp of Carabelli) on the lingual surface of the mesio-lingual cusp.
  • The presence of an oblique ridge extending from the mesiolingual cusp to the disto-buccal cusp.
  • Three well-separated and well-developed roots: two buccal and one lingual, with the lingual root being the longest.
  • Eruption time at 6 years, with first evidence of calcification at birth.

Buccal Aspect

• The crown is roughly trapezoidal, with the cervical line showing very little convexity, directed towards the root.
• Mesial outline of the crown is straight until it reaches the contact area, then convex to the tip of the cusp.
• Distal outline of the crown is convex, with the contact area located at the center of the middle third.
• Mesio-buccal cusp is broader than the disto-buccal cusp, with the mesial and distal slopes meeting at an obtuse angle, and the mesial and distal slopes of the disto-buccal cusp meeting at a right angle.

Lingual Aspect

• Semicircular distal outline from the cervical to the occlusal tip of the cusp.
• Mesial outline is the same as in the buccal aspect.
• Lingual cusps only are visible.
• Mesio-lingual cusp is the largest, accounting for 3/5 of the mesio-distal width of the crown, with an obtuse angle.
• Disto-lingual cusp accounts for 2/5 of the mesio-distal dimension, with no angle visible at the tip due to its small spheroidal smooth cusp.
• Lingual developmental groove starts at the center mesio-distally, curves sharply distally, and continues on the occlusal surface.

Mesial Aspect

• Buccal outline has a crest of curvature at the junction of the cervical third and middle, with a convex outline to the crest of curvature, then slightly concave to the junction of the middle and occlusal third, and convex again to the tip of the cusp.
• Lingual outline has a crest of curvature within the middle third, with a convex pattern until it reaches the tip of the cusp.
• Mesial marginal ridge is located at a level 1/5 the height of the crown.
• Cervical line curves occlusally about 1 mm.
• Mesial contact area is buccal to the bucco-lingual center of the crown at the junction of the occlusal and middle third.

Distal Aspect

• General outline is similar to the mesial aspect, except:
  • Bucco-lingual measurement is more mesially than distally.
  • Distal marginal ridge is located more cervically, so part of the occlusal surface is visible.
  • Curvature of the cervical line is straight zero.
  • All three roots are visible, with the distobuccal root being the smallest.
  • Distal bifurcation is 5 mm in length, while mesial aspect is 3 mm in dimension.

Occlusal Aspect

• Occlusal outline is rhomboidal, with a greater bucco-lingual measurement mesially than distally, and a greater mesio-distal measurement lingually than buccally.
• Four well-developed cusps are visible:
  • Mesio-lingual cusp is the largest.
  • Mesio-buccal cusp.
  • Disto-lingual cusp.
  • Disto-buccal cusp.
  • Cusp of Carabelli (secondary cusp).
• Mesio-buccal and disto-lingual line angles are acute, and the mesio-lingual and disto-buccal line angles are obtuse.
• Oblique ridge is formed by the union of the triangular ridge of the disto-buccal cusp and the distal ridge of the mesiolingual cusp, crossing the occlusal surface obliquely.
• Four fossae are present:
  • Mesial central fossa.
  • Linear distal fossa.
  • Mesial triangular fossa.
  • Distal triangular fossa.
• Six developmental grooves are present:
  • Central developmental groove.
  • Buccal developmental groove.
  • Distal oblique groove.
  • Lingual developmental groove.
  • Transverse groove of the oblique ridge.
  • Fifth cusp groove.
• Three pits are present:
  • Central pit.
  • Mesial pit.
  • Distal pit.

This quiz covers the characteristics and functions of permanent maxillary molars, including their roots, eruption, and role in mastication and vertical dimension.