On which tooth number is the star located in the fourth example?

On which tooth number is the star located in the fourth example?

• A. 11
• B. 9
• C. 24
• D. 14

Answer: (D)

Interpreting a star on a radiograph relies on mapping position to a tooth number using a standard system. In the widely used FDI two‑digit notation, the first digit indicates the quadrant (1 = upper right, 2 = upper left, 3 = lower left, 4 = lower right) and the second digit shows the tooth’s position from the midline in that quadrant (1 = central incisor, 2 = lateral incisor, 3 = canine, 4 = first premolar, 5 = second premolar, 6 = first molar, 7 = second molar, 8 = third molar). If the star marks the first premolar in the upper right quadrant, that tooth is the one in position 4 of quadrant 1. In the choices given, the other options would correspond to central incisors or premolars in other quadrants, while the star’s position matches the upper right first premolar. So the star is on the upper right first premolar.

Interpreting a star on a radiograph relies on mapping position to a tooth number using a standard system. In the widely used FDI two‑digit notation, the first digit indicates the quadrant (1 = upper right, 2 = upper left, 3 = lower left, 4 = lower right) and the second digit shows the tooth’s position from the midline in that quadrant (1 = central incisor, 2 = lateral incisor, 3 = canine, 4 = first premolar, 5 = second premolar, 6 = first molar, 7 = second molar, 8 = third molar). If the star marks the first premolar in the upper right quadrant, that tooth is the one in position 4 of quadrant 1. In the choices given, the other options would correspond to central incisors or premolars in other quadrants, while the star’s position matches the upper right first premolar. So the star is on the upper right first premolar.