Measurement · LLIPE
Lower lip to E-line
Loading the reference ceph.
Definition
The perpendicular distance of the lower lip (Labrale inferius) from the E-line (Prn→Pog′). Ricketts' primary lip-posture read (adult norm ≈ −2 mm).
How
Draw the E-line Prn→Pog′; drop a perpendicular from Li; negative = behind the line, positive = ahead.
Purpose
The most-quoted soft-tissue number in esthetic planning: Ricketts keyed HIS analysis to the lower lip. Ahead of the line reads lip protrusion (dental protrusion, lip trap, or short chin); well behind reads a flat, aged profile.
High
Above the norm reads as a protrusive lower lip — usually reflecting incisor protrusion or an everted lip.
Low
Below the norm reads as a retrusive lower lip — flat lower face; suggests conservative (non-retraction) mechanics.
This is a reviewed tracing on one real cephalogram — the same ceph on every page in Learn — so Lower lip to E-line here is a real reading and not a diagram.