The star marks tooth number 18.

The star marks tooth number 18.

• A. 31
• B. 28
• C. 4
• D. 18

Answer: (D)

In the Universal Numbering System used for permanent teeth, teeth are numbered 1 through 32. The upper right third molar is 1 and numbers increase across the upper arch to 16 at the upper left third molar. Then 17 starts the lower left quadrant and the sequence continues to 32 at the lower right third molar. The star is on the lower left side toward the back, which identifies the second molar in that quadrant. That tooth is numbered 18. So the marked tooth corresponds to tooth number 18. For context, other numbers would map to different teeth: for example, 31 is the lower right second molar, 28 is the lower right first premolar, and 4 is the upper left second premolar.

In the Universal Numbering System used for permanent teeth, teeth are numbered 1 through 32. The upper right third molar is 1 and numbers increase across the upper arch to 16 at the upper left third molar. Then 17 starts the lower left quadrant and the sequence continues to 32 at the lower right third molar. The star is on the lower left side toward the back, which identifies the second molar in that quadrant. That tooth is numbered 18. So the marked tooth corresponds to tooth number 18.

For context, other numbers would map to different teeth: for example, 31 is the lower right second molar, 28 is the lower right first premolar, and 4 is the upper left second premolar.