The Universal Numbering System is a form of notation used by dentists to refer to the location of each tooth in a uniform and official capacity. It breaks the mouth into four quadrants, beginning in the upper right and ending in the lower left section of the mouth.
The Universal Numbering System is the predominant tooth numbering system in the United States. Each permanent tooth is assigned a number, and the system accounts for 32 teeth. The system starts with the third molar on the upper right side of the mouth, which is a wisdom tooth. It continues across the mouth to the third molar, also a wisdom tooth, on the upper left before moving to the wisdom tooth on the lower left. If completes by moving across to the final wisdom tooth on the lower right.
The system also includes a letter-based classification for the primary dentition. This system excludes the wisdom teeth, as these teeth are often extracted or never fully emerge into the mouth. The lettering system starts with the second molar on the upper right side of the mouth, assigning it the letter "A." It continues in the same order as the numerical system, ending with letter "T" on the lower right.