Introduction to Primary and Permanent Dentitions

Overview

• Two sets of teeth in humans: deciduous (primary) and permanent teeth.
• Deciduous teeth begin developing at 14 weeks of intrauterine life, completed by age 3.
• First primary tooth erupts around 6 months, last by 28 months (±4 months).
• Mixed dentition period occurs when primary teeth shed, making way for permanent successors.

Characteristics of Teeth

• Primary Teeth (Deciduous/Milk/Baby Teeth):

  • Total of 20 in number (10 per jaw).
  • Each quadrant includes:
    • 3 Anterior Teeth: Central incisor, Lateral incisor, Canine.
    • 2 Posterior Teeth: 1st and 2nd Molars.

• Permanent Teeth:

  • Total of 32 in number (16 per jaw).
  • Each quadrant includes:
    • 1 Central incisor, 1 Lateral incisor, 1 Canine, 2 Premolars, 3 Molars.

Tooth Numbering Systems

• Purpose: Facilitate communication among dental staff.
• Three main systems:
  1. Universal Numbering System
  2. Palmer Numbering System
  3. FDI Tooth Numbering System

Universal Numbering System

• Permanent Teeth:
  • Maxillary teeth: Numbered 1-16 (right to left).
  • Mandibular teeth: Numbered 17-32 (left to right).
  • Starts with maxillary right third molar and ends at mandibular right third molar.
• Primary Teeth:
  • Numbered A-J for maxillary and K-T for mandibular, following similar sequential order.

Palmer Numbering System

• Developed by Adolf Zygmunti, later modified by Palmer.
• Divided into four quadrants by vertical and horizontal lines.
• Each quadrant has a symbol surrounding a letter or number for primary/permanent teeth.
  • Permanent teeth:
    • Tooth closest to midline = tooth 1; third molar = tooth 8.
  • Primary teeth:
    • Central incisor = A; second molar = E.
• Generally less computer-friendly than Universal System.

FDI Tooth Numbering System

• A two-digit system accepted by WHO.
• First digit represents the quadrant:
  • 1 = Maxillary right
  • 2 = Maxillary left
  • 3 = Mandibular left
  • 4 = Mandibular right
• Second digit indicates the tooth within the quadrant, starting from 1 (central incisor) to 8 (second molar).
• Primary Dentition:
  • Quadrants numbered 5-8 (clockwise).
  • Second digit 1-5 representing the tooth type.

Conclusion

• The Universal Numbering System is officially recommended by the American Dental Association since 1968 for its ease of use.

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