Features of Permanent Maxillary Central and Lateral Incisors

General Features

• Central Incisor: First tooth from the midline
• Lateral Incisor: Second tooth from the midline
• Tooth Notation: Different tooth numbers in various notation systems
• Eruption Timing: Lateral incisor erupts ~1-2 years after central incisor
• **Measurements:
  • Crown of lateral incisor is smaller in all dimensions
  • Root length is the same in both teeth
  • Relative root to crown length is greater in lateral incisor

Morphological Differences

Labial Aspect

• Outline Form: Both have trapezoidal outline forms
• **Incisal Ridge:
  • Central Incisor: Horizontal
  • Lateral Incisor: Curved
• **Angles:
  • Mesioincisal Angle: Sharp in central, slightly rounded in lateral
  • Distoincisal Angle: Rounded in central, more rounded in lateral
• **Contact Areas:
  • Central Incisor: Mesial contact in the incisal third; distal contact at junction of incisal and middle third
  • Lateral Incisor: Mesial contact at junction of incisal and middle third; distal contact in the middle third
• **Outline:
  • Mesial Outline: Straight in central, slightly convex in lateral
  • Distal Outline: Slightly convex in central, more convex in lateral
• **Surface:
  • Both have convex labial surfaces
  • More convex in lateral incisor
• **Root:
  • Single conical root in both
  • Mesiodistal diameter is less in lateral, appearing more slender
  • Apex tip shows a distal tilt in lateral incisor

Lingual Aspect

• Outline Form: Same as labial aspect
• **Ridges:
  • Incisal, mesial marginal, and distal marginal ridges more prominent in lateral incisor
• **Cingulum:
  • More convex and well-developed in lateral incisor
• **Lingual Fossa:
  • Shallow in central, deep and well-demarcated in lateral
  • W-shaped in central, V-shaped in lateral
  • Central incisor usually lacks developmental grooves/pits
  • Lateral often has developmental grooves/pits (e.g., palatoradicular or palatogingival groove)

Mesial Aspect

• **Shape:
  • Both have triangular shape and incisal ridge on midline axis
• **Labial Outline:
  • Convex in both, less convex in lateral
• Crest of Contour: Same level in both
• Labiolingual Width: Greater in lateral at incisal third due to more prominent ridges

Distal Aspect

• Differences: Same as mesial aspect
• Extra Groove: Palatoradicular or palatogingival groove if present is noticeable

Incisal Aspect

• Outline Form: Triangular in central, ovoid in lateral
• Diameters: Labiolingual and mesiodistal diameters difference
  • Central Incisor: 1.5 mm difference
  • Lateral Incisor: 0.5 mm difference

Developmental Variations

• Lateral incisor shows more variation in crown shape than any other tooth except third molar
• Example: Peg lateral (conical tubercle)
• Lateral incisors are commonly congenitally missing, second only to third molars