Differences Between Maxillary and Mandibular Incisors

Overview

• Total Incisors: 8 permanent incisors
  • 4 in maxilla
  • 4 in mandible
• Arch Trait: Tooth numbers differ for central and lateral incisors between the arches.

Aesthetic Importance

• Maxillary Incisors: More aesthetically important (incisal dominance)
• Mandibular Incisors: Less noticeable, partly hidden by maxillary incisors and lower lip

Chronology

• Eruption:
  • Mandibular central incisor erupts one year before maxillary central incisor
  • Mandibular lateral incisor erupts one year prior to maxillary lateral incisor

Measurements

• Maxillary Central Incisor: Larger than mandibular central incisor in all dimensions
• Maxillary Lateral Incisor: Smaller than mandibular lateral incisor except in mesodistal dimension
• Within the Maxillary Arch: Central incisor larger than lateral incisor
• Within the Mandibular Arch: Lateral incisor larger than central incisor

Dimensions

• Maxillary Incisors: Mesodistal diameter > Labiolingual diameter
• Mandibular Incisors: Labiolingual diameter > Mesodistal diameter

Morphological Differences by Aspect

Labial Aspect

• Horizontal Incisal Surface: All except mandibular lateral incisor (distally tilts cervically)
• Incisal Angles:
  • Maxillary incisors: Mesoincisal angle sharper than distoincisal angle
  • Mandibular incisors: Both angles equally sharp

Contact Areas

• Maxillary Incisors:
  • Central incisor: Mesial (incisal third), Distal (junction of incisal and middle third)
  • Lateral incisor: Mesial (junction of incisal and middle third), Distal (middle third)
• Mandibular Incisors: Both contact areas in the incisal third for both types

Lingual Aspect

• Characteristics similar to labial aspect differences
• Ridges and Cingulum: More prominent in maxillary incisors
• Lingual Fossa:
  • V-shaped except maxillary central incisor (W-shaped)
  • More concave and defined in maxillary incisors

Mesial Aspect

• Incisal Ridge:
  • Maxillary incisors: On midline axis
  • Mandibular incisors: Lingual to midline axis
• Labial Outline: More convex in maxillary incisors
• Lingual Outline: Cingulum more convex in maxillary incisors
• Root:
  • Maxillary incisors: Smooth and convex
  • Mandibular incisors: Developmental depression along the long axis

Distal Aspect

• Same differences as the mesial aspect

Incisal Aspect

• Dimensions:
  • Maxillary incisors: Mesodistal diameter > Labiolingual diameter
  • Mandibular incisors: Labiolingual diameter > Mesodistal diameter
• Incisal Ridge:
  • All: Horizontal and perpendicular except mandibular lateral incisor (distal side tilts lingually due to crown twist)