Dentists number teeth using a standardized system so every tooth has a fixed label that doesn’t change, regardless of whether nearby teeth are missing or restored. In the United States, the most common method is the Universal Numbering System, which assigns numbers 1 through 32 to adult teeth and letters A through T to baby teeth. Other countries use different systems, but the goal is always the same: a shorthand that lets any dental professional instantly know which tooth is being discussed.
The Universal Numbering System (1 to 32)
This is the system you’ll encounter at almost any dental office in the U.S. It starts at the back of your upper right jaw with tooth number 1 (your upper right wisdom tooth) and counts forward along the upper arch to tooth number 16 (your upper left wisdom tooth). Then it drops down to the lower left wisdom tooth, number 17, and counts forward along the lower arch all the way to tooth number 32, your lower right wisdom tooth. The numbering traces a big U-shape through your mouth.
Here’s what each number corresponds to, in pairs from right to left:
- 1 and 16: Upper third molars (wisdom teeth)
- 2 and 15: Upper second molars
- 3 and 14: Upper first molars
- 4 and 13: Upper second premolars
- 5 and 12: Upper first premolars
- 6 and 11: Upper canines (the pointed “fang” teeth)
- 7 and 10: Upper lateral incisors
- 8 and 9: Upper central incisors (your two front teeth)
- 17 and 32: Lower third molars (wisdom teeth)
- 18 and 31: Lower second molars
- 19 and 30: Lower first molars
- 20 and 29: Lower second premolars
- 22 and 27: Lower canines
- 23 and 26: Lower lateral incisors
- 24 and 25: Lower central incisors
So when your dentist says “number 19 has a cavity,” they mean your lower left first molar, one of the big chewing teeth on the bottom left side of your mouth.
What Happens When a Tooth Is Missing
A common question: if you’ve had a tooth pulled, do all the other numbers shift? They don’t. Every position keeps its assigned number permanently, even if the tooth is gone. In dental records, a missing or extracted tooth is simply marked with an “X” next to its number. If tooth 8 (one of your upper front teeth) was extracted and replaced with a bridge or implant, the chart still records it as tooth 8 with a note about the extraction and the replacement. No tooth numbers are ever left blank or reassigned.
How Baby Teeth Are Labeled
Children’s primary teeth follow the same logic but use letters instead of numbers. The 20 baby teeth are labeled A through T, starting with the upper right second molar (A) and sweeping across the upper arch to the upper left second molar (J), then dropping to the lower left second molar (K) and continuing to the lower right second molar (T). The two upper front baby teeth are E and F, and the two lower front baby teeth are O and P. Once a child starts losing baby teeth and adult teeth come in, the dentist transitions to the numbered system for those permanent teeth.
The FDI Two-Digit System
Outside the U.S., most dentists use a system developed by the FDI World Dental Federation. Instead of counting 1 to 32, it gives each tooth a two-digit code. The first digit identifies the quadrant of the mouth, and the second digit identifies the tooth’s position counting outward from the center.
The four quadrants are numbered like this:
- 1: Upper right
- 2: Upper left
- 3: Lower left
- 4: Lower right
The second digit runs 1 through 8, starting at the central incisor (1) and ending at the wisdom tooth (8). So your upper right canine is tooth 13 (quadrant 1, third tooth from center), and your lower left first molar is tooth 36 (quadrant 3, sixth tooth from center). Each digit is spoken individually: tooth 13 is said as “one-three,” not “thirteen.”
For baby teeth in this system, the quadrant numbers change to 5 through 8 (upper right is 5, upper left is 6, lower left is 7, lower right is 8), and each quadrant has teeth numbered 1 through 5.
Palmer Notation
A third system, Palmer notation, is still used by some orthodontists and oral surgeons, particularly in the UK. It numbers teeth 1 through 8 from the center of the mouth outward (just like FDI’s second digit), but instead of a quadrant number, it uses a bracket-like symbol to show which quarter of the mouth the tooth sits in. The symbol is an L-shaped line positioned to indicate upper or lower and left or right. Baby teeth use the letters A through E with the same bracket symbols.
Palmer notation works well on paper charts but is difficult to type in electronic records, which is one reason it has become less common in modern dental software.
Understanding Dental Quadrants
All three systems divide the mouth into four quadrants. The American Dental Association defines a quadrant as one of four equal sections of the dental arches, starting at the midline (the imaginary vertical line between your two front teeth) and extending back to the last tooth. The upper right, upper left, lower left, and lower right each form one quadrant, and each quadrant in a full adult mouth contains eight teeth.
When your dentist mentions a quadrant during treatment planning, they’re typically talking about a group of teeth on one side and one jaw. Deep cleanings, for example, are often scheduled one or two quadrants at a time.
Extra Teeth and Unusual Cases
Some people develop extra teeth beyond the standard 32, called supernumerary teeth. The most well-known type is a mesiodens, a small extra tooth that appears between the two upper front teeth. Others can appear behind the wisdom teeth (called distomolars) or next to molars or premolars (paramolars and parapremolars). These teeth don’t have a pre-assigned number in the Universal System since the standard chart only accounts for 32 positions. Dentists typically note them in the chart by describing their location relative to the nearest numbered tooth.