Measurement · POGNB
Pogonion to N–B (mm)
Loading the reference ceph.
Definition
The perpendicular distance from bony Pogonion (the chin's most anterior point) to the N–B line — the chin's own prominence.
How
Drop a perpendicular from Pog onto the N–B line; read in mm anterior (+) to the line.
Purpose
Isolates how much chin button the patient has beyond the mandibular base line. Balanced against L1–NB (mm): a prominent chin can 'afford' more incisor prominence; a weak chin cannot — this ratio drove Holdaway/Steiner esthetic planning.
High
Above the norm reads as a strong chin button (accommodates more incisor prominence; genioplasty rarely indicated).
Low
Below the norm reads as a weak chin button — incisor prominence shows directly in the profile.
This is a reviewed tracing on one real cephalogram — the same ceph on every page in Learn — so Pogonion to N–B (mm) here is a real reading and not a diagram.