Most dentists identify the different teeth using the Universal Numbering System, which assigns a number to each tooth in the mouth. Some orthodontists and oral surgeons instead use the Palmer Notation Method, which divides the mouth into four quadrants and assigns a number to each tooth in a quadrant.
The American Dental Association uses the Universal Numbering System for the identification of teeth. In this system, the back tooth on the top right is number 1. The system then assigns numbers to all the upper teeth, increasing from right to left.
In this system, the front two incisors are numbers 8 and 9, while the back left molar on the upper jaw is number 16. Numbering continues along the bottom jaw, this time running from left to right. Therefore, the lower left back molar is 17, while the lower right back molar is 18. The numbering is the same for children's teeth, except that the letter "d" is added to identify that a tooth as a baby tooth.
The Palmer Notation Method divides the mouth into quadrants. The tooth closest to the center of each quadrant is number 1, while the tooth closest to the back of the mouth has the number 8. Dentists identify the quadrant by drawing a rotated L-shape around each tooth number to show which quadrant it sits in, or by using the abbreviations "UR," "LR," "UL" and "LL" to identify the upper right, lower right, upper left and lower left quadrants.