Measurement · SNGOGN
SN to mandibular plane (SN-GoGn)
Loading the reference ceph.
Definition
The angle between the anterior cranial base (S–N) and the mandibular plane — Steiner's vertical-pattern read.
How
Draw S–N and the mandibular plane (Go–Me, the convention this app follows); measure the angle between them (norm ≈ 32°).
Purpose
Same clinical question as FMA (vertical vs horizontal grower) but referenced to S–N, so it stays usable when Porion/Orbitale are hard to see. >37–38° warns against mechanics that extrude molars; low values predict deep-bite relapse.
High
Above the norm reads as hyperdivergent (vertical) pattern — avoid extrusive mechanics, expect reduced overbite.
Low
Below the norm reads as hypodivergent (horizontal) pattern — deep bite, strong musculature, hard to open the bite.
This is a reviewed tracing on one real cephalogram — the same ceph on every page in Learn — so SN to mandibular plane (SN-GoGn) here is a real reading and not a diagram.