How the chart is oriented
The chart shows the teeth the way a dentist looks at the patient: the patient's right side is on the left of the chart (R), the patient's left side on the right (L). The upper jaw is at the top, the lower jaw at the bottom.
FDI two-digit notation (ISO 3950)
Every tooth has two digits. The first digit is the quadrant: 1 upper right, 2 upper left, 3 lower left, 4 lower right. Primary teeth use 5 to 8 in the same order.
The second digit counts from the midline backwards: 1 is the central incisor, 8 the third molar (wisdom tooth). Primary teeth have positions 1 to 5. Examples: 11 is the upper right central incisor, 36 the lower left first molar, 55 the upper right primary second molar.
Universal Numbering System (ADA)
The Universal Numbering System of the American Dental Association numbers the permanent teeth 1 to 32: from 1 (upper right third molar) along the upper arch to 16 (upper left third molar), then from 17 (lower left third molar) along the lower arch to 32 (lower right third molar). The number is often written with a #, e.g. #8.
Primary teeth are lettered A to T: A (upper right primary second molar) to J (upper left primary second molar), then K (lower left primary second molar) to T (lower right primary second molar).
Palmer notation
Palmer notation (after Zsigmondy) marks the quadrant with an angle symbol and counts from the midline in each quadrant: 1 to 8 for permanent teeth, A to E for primary teeth. The angle sits on the side of the midline and the occlusal plane, e.g. 6┘ for the upper right first molar and ┌6 for the lower left one.
As the angle symbols are hard to type, the chart also shows a text form: UR (upper right), UL (upper left), LL (lower left) and LR (lower right) with the tooth number, e.g. UR6 and LL6.