Functional Anatomy of Teeth - Mandibular Incisors

Mandibular Incisors

• Smaller than maxillary incisors
• Mandibular central incisor is smaller than mandibular lateral incisor, which is the reverse of the situation in maxillary 1&2
• Width is smaller than the thickness
• Mamelons are worn off soon after eruption
• Incisal ridges are inclined lingually to the root axis, which facilitates proper occlusion

Lower Central Incisor Tooth

• Crown has a fan-shaped appearance
• It's the most symmetrical tooth in the permanent dentition
• It's the smallest tooth in the permanent dentition
• Geometric outline of the crown:
  • Facial and lingual aspects have a trapezoidal outline with the smallest side cervically
  • Mesial and distal aspects have a triangular outline with the apex incisally and the base cervically
  • Incisal aspect is oval
• Surface anatomy of the crown:
  • Labial aspect: elevations (cervical ridge), depressions (shallow developmental grooves)
  • Lingual aspect: elevations (marginal ridges, cingulum), depressions (lingual fossa)
  • Proximal aspects: convex labial outline, concavo-convex lingual outline, cervical line curves incisally
• Contact areas: both mesial and distal contact areas are at the incisal one-third
• Outlines of the root: single root, apex is pointed and curved distally
• Root surface has mesial and distal developmental depressions

Lower Lateral Incisor Tooth

• Similar to lower central incisor but slightly larger
• Geometric outline of the crown:
  • Crown is twisted disto-lingually to allow the incisal ridge to follow the curve of the dental arch
  • Oval incisal aspect
• Surface anatomy of the crown:
  • Lingual aspect: elevations (marginal ridges, cingulum), depressions (lingual fossa)
  • Proximal aspects: convex labial outline, concavo-convex lingual outline, cervical line curves incisally
• Outlines of the root: single root, apex is pointed and curved distally
• Root surface has mesial and distal developmental depressions

Comparison between Lower Permanent Central and Lateral Incisors

• Tooth nomenclature: right 1, left 1 for central incisor; right 2, left 2 for lateral incisor
• Dimensions: central incisor is the smallest tooth in the permanent dentition; lateral incisor is slightly larger
• Crown: central incisor has a symmetrical bilaterally symmetrical crown; lateral incisor has an asymmetrical crown
• Labial aspect: central incisor has a straight mesial profile; lateral incisor has a curved mesial profile
• Proximal contacts: central incisor has both contact areas at the same level; lateral incisor has contact areas at different levels
• Incisal angle: central incisor has a sharp mesioincisal angle and a sharp distoincisal angle; lateral incisor has a sharp mesioincisal angle and a slightly rounded distoincisal angle
• Lingual aspect: central incisor has a centered cingulum; lateral incisor has a shifted distal cingulum
• Root: central incisor has a shorter and smaller root; lateral incisor has a longer and larger root

Canine Teeth

• Upper and lower canine teeth have different characteristics
• Upper canine:
  • General features: develops from 4 lobes, middle labial lobe is well-developed
  • Crown: bulkier, longer, and more convex
  • Labial aspect: labial surface is more convex, cusp tip is longer and more pointed
  • Lingual aspect: cingulum is centered, marginal ridges are strongly developed
  • Root: single conical root, apex is pointed
• Lower canine:
  • General features: develops from 4 lobes, middle labial lobe is not well-developed
  • Crown: narrower, shorter, and less convex
  • Labial aspect: labial surface is less convex, cusp tip is shorter and less pointed
  • Lingual aspect: cingulum is centered, marginal ridges are less developed
  • Root: single root, apex is pointed and curved distally

This quiz covers the anatomy of mandibular incisors, including their size, shape, and features. Learn about the differences between mandibular and maxillary incisors.