Measurement · NLA
Nasolabial angle
Loading the reference ceph.
Definition
The angle at Subnasale between the base of the nose and the upper lip — here measured Prn-Sn-Ls (pronasale is used for the nasal ray since the columella point is not landmarked; treat as approximate).
How
At Subnasale (Sn, where nose meets lip), measure the angle between Sn→Prn (up the nose) and Sn→Ls (down the upper lip). Classic norm ≈ 90–110°.
Purpose
The gatekeeper for upper-incisor retraction: retracting upper incisors rotates the lip back and OPENS this angle. An already-obtuse NLA warns that further retraction will flatten and age the profile; an acute NLA tolerates (or invites) retraction.
High
Above the norm reads as an obtuse nasolabial angle — retracted/thin upper lip; avoid further incisor retraction.
Low
Below the norm reads as an acute nasolabial angle — protrusive upper lip/incisors; retraction has room to improve the profile.
This is a reviewed tracing on one real cephalogram — the same ceph on every page in Learn — so Nasolabial angle here is a real reading and not a diagram.