Three systems are in active use, and they disagree. The same tooth is 19, 36 or lower-left-6 depending on who wrote the chart — and the same written number can point at two different teeth.
United States
One continuous run of numbers, 1 to 32, starting at the upper right third molar, across the upper arch to the upper left third molar (16), then dropping to the lower left third molar (17) and running back to the lower right third molar (32). Primary teeth use A to T in the same direction.
19 = lower left first molar
International
Two digits. The first is the quadrant — 1 upper right, 2 upper left, 3 lower left, 4 lower right — and the second is the position counted outward from the midline, 1 for the central incisor through 8 for the third molar. Primary teeth reuse the scheme with quadrants 5 to 8.
36 = quadrant 3, position 6 = lower left first molar
Orthodontics, UK practice
The tooth number 1 to 8 is written inside a right-angle symbol. The horizontal arm stands for the occlusal plane and the vertical arm for the midline, so the corner points at the quadrant. Primary teeth use A to E in the same brackets.
┌6 = lower left first molar
All 32 permanent teeth. Note the direction change: in the upper left and lower right quadrants the two systems count the same way, and in the upper right and lower left they count in opposite directions.
| Universal | FDI | Palmer | Tooth | Universal | FDI | Palmer | Tooth |
|---|---|---|---|---|---|---|---|
| 1 | 18 | 8┘ | upper right third molar | 17 | 38 | ┌8 | lower left third molar |
| 2 | 17 | 7┘ | upper right second molar | 18 | 37 | ┌7 | lower left second molar |
| 3 | 16 | 6┘ | upper right first molar | 19 | 36 | ┌6 | lower left first molar |
| 4 | 15 | 5┘ | upper right second premolar | 20 | 35 | ┌5 | lower left second premolar |
| 5 | 14 | 4┘ | upper right first premolar | 21 | 34 | ┌4 | lower left first premolar |
| 6 | 13 | 3┘ | upper right canine | 22 | 33 | ┌3 | lower left canine |
| 7 | 12 | 2┘ | upper right lateral incisor | 23 | 32 | ┌2 | lower left lateral incisor |
| 8 | 11 | 1┘ | upper right central incisor | 24 | 31 | ┌1 | lower left central incisor |
| 9 | 21 | └1 | upper left central incisor | 25 | 41 | 1┐ | lower right central incisor |
| 10 | 22 | └2 | upper left lateral incisor | 26 | 42 | 2┐ | lower right lateral incisor |
| 11 | 23 | └3 | upper left canine | 27 | 43 | 3┐ | lower right canine |
| 12 | 24 | └4 | upper left first premolar | 28 | 44 | 4┐ | lower right first premolar |
| 13 | 25 | └5 | upper left second premolar | 29 | 45 | 5┐ | lower right second premolar |
| 14 | 26 | └6 | upper left first molar | 30 | 46 | 6┐ | lower right first molar |
| 15 | 27 | └7 | upper left second molar | 31 | 47 | 7┐ | lower right second molar |
| 16 | 28 | └8 | upper left third molar | 32 | 48 | 8┐ | lower right third molar |
Derived from the ADA Universal sequence and the FDI/ISO 3950 quadrant scheme. Every row is covered by an automated test in the site's build.
Universal runs 1–32. FDI permanent numbers are 11–18, 21–28, 31–38 and 41–48. Where those overlap, a bare number is valid in both systems and identifies a different tooth in each.
| Number | Read as Universal | Read as FDI |
|---|---|---|
| 11 | upper left canine | upper right central incisor (Universal 8) |
| 12 | upper left first premolar | upper right lateral incisor (Universal 7) |
| 13 | upper left second premolar | upper right canine (Universal 6) |
| 14 | upper left first molar | upper right first premolar (Universal 5) |
| 15 | upper left second molar | upper right second premolar (Universal 4) |
| 16 | upper left third molar | upper right first molar (Universal 3) |
| 17 | lower left third molar | upper right second molar (Universal 2) |
| 18 | lower left second molar | upper right third molar (Universal 1) |
| 21 | lower left first premolar | upper left central incisor (Universal 9) |
| 22 | lower left canine | upper left lateral incisor (Universal 10) |
| 23 | lower left lateral incisor | upper left canine (Universal 11) |
| 24 | lower left central incisor | upper left first premolar (Universal 12) |
| 25 | lower right central incisor | upper left second premolar (Universal 13) |
| 26 | lower right lateral incisor | upper left first molar (Universal 14) |
| 27 | lower right canine | upper left second molar (Universal 15) |
| 28 | lower right first premolar | upper left third molar (Universal 16) |
| 31 | lower right second molar | lower left central incisor (Universal 24) |
| 32 | lower right third molar | lower left lateral incisor (Universal 23) |
Numbers 1–10, 19, 20, 29 and 30 exist only in Universal. Numbers 33–38 and 41–48 exist only in FDI. Seeing any of those elsewhere on a chart tells you which system it uses.
Twenty primary teeth, lettered A to T in the Universal system and numbered 51 to 85 in FDI. Letters and numbers cannot be confused with each other, so primary notation is never ambiguous between the two systems.
| Universal | FDI | Tooth |
|---|---|---|
| A | 55 | upper right primary second molar |
| B | 54 | upper right primary first molar |
| C | 53 | upper right primary canine |
| D | 52 | upper right primary lateral incisor |
| E | 51 | upper right primary central incisor |
| F | 61 | upper left primary central incisor |
| G | 62 | upper left primary lateral incisor |
| H | 63 | upper left primary canine |
| I | 64 | upper left primary first molar |
| J | 65 | upper left primary second molar |
| K | 75 | lower left primary second molar |
| L | 74 | lower left primary first molar |
| M | 73 | lower left primary canine |
| N | 72 | lower left primary lateral incisor |
| O | 71 | lower left primary central incisor |
| P | 81 | lower right primary central incisor |
| Q | 82 | lower right primary lateral incisor |
| R | 83 | lower right primary canine |
| S | 84 | lower right primary first molar |
| T | 85 | lower right primary second molar |