Dentists, hygienists, insurers and dental software all need to agree on exactly which tooth is which. This page explains the three numbering systems you will meet, how adult and baby teeth differ, and how to convert between systems.
Contents
- Why teeth are numbered
- Reading a chart: the patient’s right is on your left
- Universal numbering system
- FDI / ISO 3950 system
- Palmer notation
- Baby teeth and mixed dentition
- Adult tooth conversion table
- Baby tooth conversion table
- Extra (supernumerary) teeth
Why teeth are numbered
A tooth number is a short, unambiguous name. “#3” is quicker to write than “upper right first molar,” and it lets your dentist, your insurer and a specialist all point to the same tooth. The catch is that different countries use different systems, so the same tooth can be called 3, 16 or 6┘.
Reading a chart: the patient’s right is on your left
Dental charts are drawn as if you are standing in front of the patient, looking at them. So the patient’s right side appears on the left of the chart. This is the single most common source of confusion for new students. “Right” and “left” always mean the patient’s right and left.
The mouth is divided into four quadrants: upper right, upper left, lower left and lower right. Within each quadrant, teeth are counted from the midline (front) toward the back.
Universal numbering system
The Universal system is approved by the American Dental Association and is the standard in the United States, including on dental claim forms.
- Adult teeth: 1–32. Counting starts at the patient’s upper right third molar (#1), goes across the upper arch to the upper left third molar (#16), drops down to the lower left third molar (#17) and goes back across to the lower right third molar (#32).
- Baby teeth: A–T. Same path: A is the upper right second molar, J the upper left second molar, K the lower left second molar and T the lower right second molar.
- Wisdom teeth are always 1, 16, 17 and 32, even if they are missing. Numbers never shift when a tooth is lost.
FDI / ISO 3950 system
The FDI World Dental Federation system (also published as ISO 3950) is used in most countries outside the US and is recommended by the WHO. Each tooth gets two digits:
- First digit = quadrant. Adult: 1 upper right, 2 upper left, 3 lower left, 4 lower right. Baby: 5, 6, 7, 8 in the same order.
- Second digit = tooth, counted from the midline: 1 central incisor through 8 third molar (1–5 for baby teeth).
- Say each digit separately: 26 is “two-six,” not “twenty-six.” It is the upper left first molar.
Palmer notation
Palmer (Zsigmondy–Palmer) notation is common in the UK and in orthodontics. It draws a small bracket to show the quadrant, with the tooth number inside:
- Adult teeth are numbered 1–8 from the midline; baby teeth are lettered A–E.
- The bracket is the corner of a cross dividing the mouth: 6┘ is the upper right first molar, └6 upper left, ┌6 lower left, 6┐ lower right.
- Because the symbols are hard to type, software often writes Palmer as UR6, UL6, LL6, LR6.
Baby teeth and mixed dentition
Children have 20 primary teeth: in each quadrant a central incisor, lateral incisor, canine, first molar and second molar. There are no premolars or third molars in the baby set. The adult premolars grow in where the baby molars were, and the adult first molars (the “six-year molars”) come in behind the baby teeth without replacing anything.
From about age 6 to 12 a child has mixed dentition, both baby and adult teeth at once. Charts then use letters (Universal), 5–8 quadrants (FDI) or A–E (Palmer) for the baby teeth and numbers for the adult teeth. See mixed dentition in 3D and move the age slider from 6 to 12 to watch baby teeth fall out and adult teeth come in.
Interactive chart
Adult tooth conversion table
Baby tooth conversion table
| Universal | FDI | Palmer | Tooth | Erupts | Falls out |
|---|---|---|---|---|---|
| A | 55 | E┘ | Upper right second molar | 25-33 mos | 10-12 yrs |
| B | 54 | D┘ | Upper right first molar | 13-19 mos | 9-11 yrs |
| C | 53 | C┘ | Upper right canine | 16-22 mos | 10-12 yrs |
| D | 52 | B┘ | Upper right lateral incisor | 9-13 mos | 7-8 yrs |
| E | 51 | A┘ | Upper right central incisor | 8-12 mos | 6-7 yrs |
| F | 61 | └A | Upper left central incisor | 8-12 mos | 6-7 yrs |
| G | 62 | └B | Upper left lateral incisor | 9-13 mos | 7-8 yrs |
| H | 63 | └C | Upper left canine | 16-22 mos | 10-12 yrs |
| I | 64 | └D | Upper left first molar | 13-19 mos | 9-11 yrs |
| J | 65 | └E | Upper left second molar | 25-33 mos | 10-12 yrs |
| K | 75 | ┌E | Lower left second molar | 23-31 mos | 10-12 yrs |
| L | 74 | ┌D | Lower left first molar | 14-18 mos | 9-11 yrs |
| M | 73 | ┌C | Lower left canine | 17-23 mos | 9-12 yrs |
| N | 72 | ┌B | Lower left lateral incisor | 10-16 mos | 7-8 yrs |
| O | 71 | ┌A | Lower left central incisor | 6-10 mos | 6-7 yrs |
| P | 81 | A┐ | Lower right central incisor | 6-10 mos | 6-7 yrs |
| Q | 82 | B┐ | Lower right lateral incisor | 10-16 mos | 7-8 yrs |
| R | 83 | C┐ | Lower right canine | 17-23 mos | 9-12 yrs |
| S | 84 | D┐ | Lower right first molar | 14-18 mos | 9-11 yrs |
| T | 85 | E┐ | Lower right second molar | 23-31 mos | 10-12 yrs |
Extra (supernumerary) teeth
Some people have extra teeth. In the Universal system, extra adult teeth are numbered 51–82, which is the nearest normal tooth number plus 50 (an extra tooth next to #1 is #51). Extra baby teeth add an S to the nearest letter (AS–TS). Note that FDI also uses 51–85, but for ordinary baby teeth, so always check which system a chart is using.
Sources: American Dental Association Universal Tooth Designation System; FDI World Dental Federation / ISO 3950. For education only, not medical advice.