Using the Universal Numbering System, read the molar furthest back on the top left hand side of the jaw diagram as number one, then number each tooth on the top of the jaw in ascending order from left to right, according to Aetna. The furthest molar on the top right is usually number 16. After reaching this tooth, read each tooth on the bottom jaw in ascending order from right to left.
The Universal Numbering System is the type of tooth diagram that dentists in the American Dental Association use, states Aetna. This system assigns a number between one and 32 to each tooth in the mouth. The Universal Numbering System counts both extracted and lost teeth. For example, if a patient no longer has his wisdom teeth, the existing molar at the top left end of the jaw is number two.
Orthodontists and dental specialists more often use the Palmer Notation Method. This numbering system divides the mouth into four quadrants, representing the top, bottom, right and left sides of the jaw, as shown on DentalCare.com. Each tooth in a quadrant has a number from one through eight, beginning with the middle incisor and working toward the molars. The top right incisor on a Palmer diagram is number 12, meaning that it is the first tooth in the second quadrant.