Primary and permanent dentition and FDI tooth numbering
- Anatomy and histology
Children have 20 primary teeth and adults 32 permanent teeth. The FDI two-digit system names each tooth by quadrant and position.
See it in 3D: Upper right central incisor · Lower left first molar
What it is
Humans have two sets of teeth. The primary (deciduous) dentition has 20 teeth: in each quadrant two incisors, one canine and two molars. The permanent dentition has 32: in each quadrant two incisors, one canine, two premolars and three molars, the last being the third molar (wisdom tooth). Premolars replace the primary molars; the permanent molars erupt behind them with no predecessor. The FDI (World Dental Federation) system, used in Colombia and most of the world, gives each tooth two digits: the quadrant, then the position from the midline.
Clinical anatomy
- Permanent quadrants: 1 upper right, 2 upper left, 3 lower left, 4 lower right (as seen facing the patient, the patient's right is on the viewer's left).
- Primary quadrants: 5 upper right, 6 upper left, 7 lower left, 8 lower right.
- Second digit: 1–2 incisors, 3 canine, 4–5 premolars (or primary molars), 6–8 molars.
- Examples: 11 is the upper right central incisor; 36 is the lower left first permanent molar; 85 is the lower right second primary molar.
- The universal system used in the United States numbers permanent teeth 1 to 32 instead; check which system a record uses.
Clinical correlation
- Writing the wrong tooth number is a classic cause of wrong-tooth extraction: confirm the number, the side and the radiograph.
- Missing teeth (hypodontia, most often third molars, upper lateral incisors and lower second premolars) and extra teeth (a mesiodens between the upper central incisors) change the count.
- Dental charts and radiographs are used in forensic identification because the pattern of teeth and restorations is individual.
Next step / Initial management
- Record findings with the FDI number and the surface involved, so the dentist can act on them.
- A primary tooth that does not fall out, or a permanent tooth that does not appear long after the expected age: request a radiograph through the dentist to look for a missing or impacted tooth.
- Refer to the dentist or orthodontist when a tooth is missing, extra or clearly out of place.
Test yourself
Think of the answer, then tap the question to see it.
How many primary and how many permanent teeth are there?
20 primary (deciduous) teeth and 32 permanent teeth.
In the FDI system, which tooth is 36?
The lower left first permanent molar (quadrant 3, position 6).
Which primary teeth do the permanent premolars replace?
The primary molars; the permanent molars erupt behind them with no predecessor.
Elsewhere in DurgiPedia
Connections
See it in 3D2
The structures of Durgical's 3D anatomy where it is found.
Educational content; it does not replace assessment by a dentist or doctor and is not a clinical instruction. For facial or neck swelling with difficulty swallowing or breathing, a knocked-out tooth or bleeding that will not stop, go to an emergency department at once.
Sources: Anatomy, Permanent Dentition (StatPearls Publishing (NCBI Bookshelf), 2023); Anatomy, Head and Neck, Teeth (StatPearls Publishing (NCBI Bookshelf), 2023); Developmental Disturbances of the Teeth, Anomalies of Number (StatPearls Publishing (NCBI Bookshelf), 2025).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.