Which set of landmarks is used to measure facial thirds?

Which set of landmarks is used to measure facial thirds?

• A. Tr- Of; Of- Sn; Sn- Pg
• B. Tr- N; N- Sn; Sn- Pg
• C. Tr- Of; Of- Sn; Sn- Gn
• D. Tr- N; N- Sn; Sn- Gn

Answer: (D)

Dividing the face into three vertical thirds uses stable midline landmarks from the hairline down to the chin so proportions can be assessed consistently. The upper third runs from Trichion (the hairline point) to Nasion (the nasal bridge), the middle third from Nasion to Subnasale (where the base of the nose meets the upper lip), and the lower third from Subnasale to Gnathion (a midline point on the chin). This combination—Tr-N, N-Sn, and Sn-Gn—provides three equal segments that reflect the forehead, midface, and lower face in a repeatable way. Gnathion marks the chin’s lowest midline point, making Sn-Gn a reliable lower-third endpoint across individuals. Other endpoints (like Pogonion or orbitale-related points) can vary with soft-tissue contour or do not define the standard vertical thirds, so they aren’t used for this measurement.

Dividing the face into three vertical thirds uses stable midline landmarks from the hairline down to the chin so proportions can be assessed consistently. The upper third runs from Trichion (the hairline point) to Nasion (the nasal bridge), the middle third from Nasion to Subnasale (where the base of the nose meets the upper lip), and the lower third from Subnasale to Gnathion (a midline point on the chin). This combination—Tr-N, N-Sn, and Sn-Gn—provides three equal segments that reflect the forehead, midface, and lower face in a repeatable way. Gnathion marks the chin’s lowest midline point, making Sn-Gn a reliable lower-third endpoint across individuals. Other endpoints (like Pogonion or orbitale-related points) can vary with soft-tissue contour or do not define the standard vertical thirds, so they aren’t used for this measurement.