FDI Two-Digit Tooth Numbering System: Comprehensive Student Guide

Why Every Dental Student Must Master FDI Notation

The FDI ISO-3950 two-digit notation is used globally in dental clinical records, journal literature, and dental board examinations. It provides a simple, unambiguous method to communicate exact tooth locations.

Decoding the First Digit: Quadrants

The first digit identifies the quadrant of the mouth starting from the upper right maxillary quadrant and moving clockwise:

• Digit 1: Permanent Upper Right (Maxillary Right)
• Digit 2: Permanent Upper Left (Maxillary Left)
• Digit 3: Permanent Lower Left (Mandibular Left)
• Digit 4: Permanent Lower Right (Mandibular Right)
• Digit 5: Primary Upper Right
• Digit 6: Primary Upper Left
• Digit 7: Primary Lower Left
• Digit 8: Primary Lower Right

Decoding the Second Digit: Tooth Position

The second digit represents the tooth's relative distance from the central midline (1 = Central Incisor, 8 = Third Molar):

• 1: Central Incisor
• 2: Lateral Incisor
• 3: Canine (Cuspid)
• 4: First Premolar / First Primary Molar
• 5: Second Premolar / Second Primary Molar
• 6: First Permanent Molar
• 7: Second Permanent Molar
• 8: Third Molar (Wisdom Tooth)

Clinical Example: Identifying Tooth 36

First digit 3 = Lower Left Quadrant. Second digit 6 = First Permanent Molar. Therefore, 36 refers to the Mandibular Left First Permanent Molar.

Frequently Asked Questions (FAQs)