Numbering systems have been developed in order to have a standard way of referring to particular teeth (there are more than 32 different systems). Two are commonly in use in the US today:
- the Universal Numbering System has been adopted by the American Dental Association and is in use by most general dentists today, and
- the Palmer Notation Method is used by some orthodontists, pedodontists (child dental specialist), and oral surgeons (originally called the Zsigmondy system after an Austrian dentist of that name who developed the idea in 1861).
Internationally the two-digit FDI World Dental Federation notation is widely used.
Universal Numbering System
Tooth number 1 is the tooth farthest back on the right side of your mouth in the upper (maxillary) jaw.
Numbering continues along your upper teeth toward the front and across to the tooth farthest back on the top left side (which is number 16).
The numbers continue by dropping down to the lower (mandibular) jaw. Number 17 is the tooth farthest back on the left side of your mouth on the bottom.
Numbering continues again toward the front and across to the tooth farthest back on the bottom right side of your mouth (which is number 32).
In this system, the teeth that should be there are numbered. If you are missing your wisdom teeth, your first number will be 2 instead of 1, acknowledging the missing tooth. If you’ve had teeth removed or teeth are missing, the missing teeth will be numbered as well.
In the original system, children’s 20 primary teeth are numbered in the same order, except that a small letter “d” follows each number to indicate deciduous (primary) teeth. So, a child’s first tooth on the upper right would be 1d and the last tooth on the lower right would be 20d.
However, most dentists and insurance companies now use a modified version of the Universal Numbering System for children. This version uses the letters A through T instead of the number 1 through 20. So, a child’s first tooth on the upper right would be A and the last tooth on the lower right would be T.
Palmer Notation Method
In this system, the mouth is divided into four sections called quadrants. The numbers 1 through 8 and a unique symbol are used to identify the teeth in each quadrant. The numbering runs from the center of the mouth to the back.
In the upper right section of the mouth, for example, tooth number 1 is the incisor (flat, front tooth) just to the right of the center of the mouth. The numbers continue to the right and back to tooth number 8, which is the wisdom tooth (third molar.)
The numbers sit inside an L-shaped symbol used to identify the quadrant. The “L” is right side up for the teeth in the upper right. The teeth in the upper left use a backward “L.” For the bottom quadrants, the “L” is upside-down. The quadrants may also be identified by letters, such as “UR” or “URQ” for the upper right quadrant.
In children, the Palmer Notation System uses uppercase letters instead of numbers. Following the same order as for adult’s teeth, children’s 20 primary teeth are lettered “A” through “E” in each quadrant. The same symbol is used to identify the quadrants.
FDI Two-Digit Notation
In the FDI (Federation Dentaire Internationale) World Dental Federation ISO-3950 notation 1s are central incisors, 2s are laterals, 3s are canines, 4s are 1st premolars etc., up through 8s which are 3rd molars. The permanent teeth quadrants are designated 1 to 4 such that 1 is upper right, 2 is upper left, 3 is lower left and 4 is lower right, with the resulting tooth identification a two-digit combination of the quadrant and tooth (e.g. the upper right central incisor is 11 and the left is 21). The lower left permanent first molar is 36; however, it is not said thirty-six, but rather three six. 11 is one one, not eleven.
The currently accepted convention to view the FDI notation chart is from the perspective of the patient’s right on the left:
In the deciduous dentition the numbering is correspondingly similar except that the quadrants are designated 5,6,7 and 8.
Thanks to Dr. John Webster BDS, Australia for his clarification on the FDI notation system.
Comparison of Tooth Numbering Systems
|The orientation of the teeth below is merely for comparison (e.g. the accepted orientation for the FDI Two-Digit system is as above: patient’s right on the left).|
*baby teeth, aka primary teeth, deciduous teeth, or milk teeth