Dental Anatomy: Tooth Morphology

Human Dentition

• Human teeth are equally arranged into four quadrants: upper right, upper left, lower right, and lower left.
• Each quadrant has a specific arrangement of teeth: incisors, canines, premolars, and molars.

Tooth Morphology

• Incisors:
  • Have a trapezoidal shape with the longer parallel side at the incisal edge and the shorter side at the cementoenamel junction.
  • Labial and lingual crest of curvatures are at the cervical third of the crown.
  • Newly erupted incisors have rounded portions on the incisal ridge called "Mamelons".
• Canines:
  • Have a cone or wedge shape, suitable for piercing, cutting, and tearing.
  • Are designed to function as holding or grasping teeth.
• Premolars (Bicuspids):
  • Have a wider surface with multiple projections (cusps), suitable for grinding food.
  • The fourth tooth from the midline is the First Premolar, and the fifth tooth is the Second Premolar.
• Molars:
  • Have a wide surface with multiple projections (cusps), suitable for grinding food.
  • Are characterized by having multiple cusps.

Tooth Development

• Developmental Lobes:
  • Are the first growth centers of the tooth, which fuse to form the tooth.
  • Each tooth begins its development from four or more growth centers.
• Developmental Grooves:
  • Are the lines that mark the fusion of the developmental lobes.
  • Can be seen on the tooth after its eruption but soon disappear due to wear and attrition.

Tooth Structure

• Pulp Chamber:
  • Is wider from the mesio-distal section, confirming the shape of the crown.
  • Tapers from the incisal part, but is wider at the cervix.
  • Has three pulp horns corresponding to the three mamelons.
• Root Canal:
  • Tapers towards the apex.
  • Has a roughly triangular shape in young teeth, becoming rounded or crescent-shaped in old teeth.
• Cervical Line:
  • Is less curved than that of the central incisor.
  • Is perfectly centered.

Other Terms

• Inclined Planes:
  • Are slopes from cusp tips to the developmental grooves.
• Height of Contour:
  • Is the point of maximum convexity of the tooth surface.
• Pits:
  • Are small pinpoint depressions located at the junction of developmental grooves and/or at their terminals.