A dental tooth number chart is a chart that identifies each tooth according to the Universal Numbering System. This system was adopted by the American Dental Association which is generally used by dentists. The Palmer Notation Method is another numbering system, commonly used by oral surgeons.
With the Universal Numbering System, tooth number one is the tooth farthest back on the right side of the mouth, in the upper jaw. The numbering then continues along the upper teeth toward the front of the mouth, back to the tooth that's farthest back on the top-left side. That last is number 16.
The numbers then drop to the lower jaw. Tooth number 17 is the tooth that is on the left side of the mouth, farthest back. From there the numbering continues towards the front of the mouth and across to the tooth that is on the right side of the mouth, and that tooth is number 32.
For the Palmer Notation, tooth number one is the incisor tooth that is just to the right of the center of the mouth. The numbers then continue to the right and then back to the wisdom molar, which is tooth number eight. For that tooth number chart, the numbers are inside an L-shaped symbol that is used to identify the quadrant. The quadrants are sometimes identified by letters, meaning URQ would refer to the upper-right quadrant.