Which landmark pair is used to calculate the facial index?

• A. Of- Gn and Au- Au
• B. N- Gn and Go- Go
• C. Of- Pg and Au- Au
• D. N- Gn and Zy- Zy

Answer: (D)

The facial index measures how tall the face is compared to how wide it is. To get those dimensions, you use the vertical height from Nasion to Gnathion (N-Gn) for the facial height, and the horizontal width across the cheeks between the Zygaions on each side (Zy-Zy) for the facial width. The index is calculated as (N-Gn) divided by (Zy-Zy) times 100. This combination directly captures the standard height-to-width relationship of the face, so using N-Gn for height and Zy-Zy for width is the correct approach. Other landmark pairs don’t reflect the conventional width measurement or the standard vertical height needed for this index.