The ISO-3950 system is a two-digit notation system where the first digit describes the quadrant:

• Upper right quadrant (maxillary) - 5
• Upper left quadrant (maxillary) - 6
• Lower left quadrant (mandibular) - 7
• Lower right quadrant (mandibular) - 8

The second digit corresponds to the sequence number for each tooth in a quadrant:

• Medial (central) incisors - 1
• Lateral incisors - 2
• Canines - 3
• First molars - 4
• Second molars - 5

For example, the primary lateral incisor in the lower left quadrant has a numbering of 72 where:

• 7 is used for describing the lower left quadrant;
• 2 refers to the lateral incisor as it is the second tooth from the midline of the lower jaw.