Maxillary Premolar and Molar Root Canal Anatomy

Posted on Apr 24, 2025 in Biology

Maxillary Second Premolar Anatomy

This tooth typically has one root (88%) or two roots (12%). Root canal configurations within a single root can vary:

  • Type I (One canal): 53%
  • Type II (Two canals merging into one): 22%
  • Type III (Two separate canals): 12%

One, two, or three canals can occur within a single root, although the incidence of three canals is low (1%). The majority of teeth have a single canal extending to the apex.

Buccal View (Recently Calcified)

A view of a recently calcified second premolar with a large pulp reveals:

  1. Narrow mesiodistal width of the pulp.
  2. Apical-distal curvature.
  3. Distal-axial inclination of the tooth.

Mesial View (Recently Calcified)

The same tooth viewed mesially demonstrates:

  1. Broad buccolingual width, revealing the pulp to be “ribbon-shaped”.
  2. A single root with a large single canal.
  3. Buccal-axial angulation of the tooth.

Cross-Sections (Recently Calcified)

Cross-sections at three levels show:

  1. Cervical level: The pulp is very large in a young tooth, wide buccolingually. The canal orifice is centered (Oval to ovoid shape).
  2. Midroot level: The canal remains ovoid in shape.
  3. Apical third level: The canal becomes round in shape.

Buccal View (Pulp Recession)

A buccal view of a premolar with pulp recession reveals:

  1. Pulp recession and a “thread-like” appearance of the pulp.
  2. Two roots.
  3. Bayonet curve of the roots (occurs approximately 20% of the time).
  4. Distal-axial inclination of the tooth.

Mesial View (Pulp Recession)

The same tooth viewed mesially demonstrates:

  1. Buccolingual width revealing the coronal pulp to be “ribbon-shaped” rather than “thread-like”.
  2. High bifurcation and two separate roots in the apical third.
  3. Lingual-axial angulation of the tooth.

Cross-Sections (Pulp Recession)

Cross-sections at three levels show:

  1. Cervical level: The chamber is a very narrow oval to ovoid shape, extending deeply into the root.
  2. Midroot level: The bayonet curve and round canal orifices are apparent.
  3. Apical third level: The canals are round.

Maxillary First Molar Anatomy

Root canal variations:

  • 40% have 3 root canals within 3 roots.
  • 60% have 4 canals (2 canals within the mesiobuccal root).
  • When 2 canals are present in the mesiobuccal root, they exit through one foramen 80% of the time and two separate foramina 20% of the time.

Buccal View (Recently Calcified)

A radiograph of a recently calcified first molar with a large pulp will reveal:

  1. A large pulp chamber.
  2. Mesiobuccal root potentially with two separate canals; distobuccal and palatal roots each typically with one canal.
  3. Slightly curved buccal roots.
  4. Slightly curved palatal root.
  5. Vertical axial alignment of the tooth.

Mesial View (Recently Calcified)

The same tooth viewed mesially demonstrates:

  1. Buccolingual width of the pulp chamber.
  2. Apical-buccal curvature of the palatal root (occurs approximately 55% of the time).
  3. Buccal inclination of the buccal roots.

Cross-Sections (Recently Calcified)

Cross-sections at two levels show:

  1. Cervical level: The pulp is very large in a young tooth, typically triangular in shape. If a fourth canal is present, the shape becomes rhomboidal with rounded ends.
  2. Apical third level: The canals are essentially round.

Maxillary Second Molar Anatomy

Root and canal variations:

  • 60% have 3 root canals within 3 roots.
  • 40% have 4 canals (typically 2 canals within the mesiobuccal root).
  • When 2 canals are present in the mesiobuccal root, they exit through one foramen 65% of the time and two separate foramina 35% of the time.
  • 25% have 2 roots (containing either 2 or 3 root canals).
  • 15% have 1 root.

Buccal View (Recently Calcified)

A radiograph of a recently calcified second molar with a large pulp will reveal:

  1. A large pulp chamber.
  2. Mesiobuccal, distobuccal, and palatal roots, often each with one canal (unless variations are present).
  3. Gradual curvature of all three canals.

Cross-Sections (Recently Calcified)

Cross-sections at two levels show:

  1. Cervical level: The pulp is very large in a young tooth. The chamber shape is typically triangular, becoming rhomboidal with rounded ends if four canals are present.
  2. Apical third level: The canals are essentially round.