The star marks tooth number 4.

The star marks tooth number 4.

• A. 31
• B. 28
• C. 4
• D. 18

Answer: (C)

The key idea is that tooth numbering schemes differ, so recognizing which system is being used on the image is essential. In dentistry, a single-digit tooth number is a hallmark of the Universal Numbering System, where permanent teeth are numbered from 1 to 32 starting at the upper-right third molar and moving across to the upper left, then down the lower arch to the lower right. If the star is labeling a lone digit, that signals we’re using the Universal System. The fourth tooth in that sequence is the upper right second premolar. So the star-marked tooth corresponds to that position, which is why the straightforward digit 4 is the correct way to refer to it in this context. The other numbers shown would belong to a different notation method (two-digit codes used in the FDI system), and would correspond to different teeth, not the one simply labeled with a single digit.

The key idea is that tooth numbering schemes differ, so recognizing which system is being used on the image is essential. In dentistry, a single-digit tooth number is a hallmark of the Universal Numbering System, where permanent teeth are numbered from 1 to 32 starting at the upper-right third molar and moving across to the upper left, then down the lower arch to the lower right.

If the star is labeling a lone digit, that signals we’re using the Universal System. The fourth tooth in that sequence is the upper right second premolar. So the star-marked tooth corresponds to that position, which is why the straightforward digit 4 is the correct way to refer to it in this context. The other numbers shown would belong to a different notation method (two-digit codes used in the FDI system), and would correspond to different teeth, not the one simply labeled with a single digit.