Lips measurement
Steiner S-Line
Runs from the middle of the nose’s lower “S” curve (between tip and subnasale) to the chin. Both lips should just touch it; protrusion and retrusion are penalised equally.
At a glance
- Ideal
- Both lips 0 mm (on the line)
- Unit
- millimetres
- Weight in the overall score
- 3
- Area
- Lips
How it is measured
Distance of Ls and Li from the line mid(Prn,Sn)–Pog
- Prn Pronasale (nose tip) — The most forward point of the nasal tip.
- Sn Subnasale — The point where the underside of the nose meets the upper lip.
- Pog Pogonion — The most forward point of the chin.
- Ls Labrale superius (upper lip) — The most forward point of the upper lip.
- Li Labrale inferius (lower lip) — The most forward point of the lower lip.
Ideal range and tiers
Each value falls into a tier (T1 = ideal). Comfortably inside T1 the rating is 10, easing to 9.5 at the edges of the ideal range; beyond it the rating falls with the deviation — fastest in the first tiers outside the ideal — down to 0 at the far end of the worst tier.
| Tier | Range | Rating |
|---|---|---|
| T1 Ideal | −1.5 to 1.5 mm | 9.5–10 |
| T2 Acceptable | −3.5 to −1.5 mm or 1.5–3.5 mm | 4.3–9.5 |
| T3 Poor | < −3.5 mm or > 3.5 mm | 0–4.3 |
| Tier | Range | Rating |
|---|---|---|
| T1 Ideal | −1.5 to 1.5 mm | 9.5–10 |
| T2 Acceptable | −3.5 to −1.5 mm or 1.5–3.5 mm | 4.3–9.5 |
| T3 Poor | < −3.5 mm or > 3.5 mm | 0–4.3 |
Differences between populations
Optional population norms move this range by the difference reported between groups measured the same way:
- East Asian: upper lip +5.5 mm; lower lip men +5 mm, women +4.5 mm.
- African descent: upper lip +4 mm; lower lip +4 mm (Assumed equal to the E-line difference.).
Individual faces vary far more within any group than between groups; these are averages, not targets.
Related measurements
References
- Steiner CC. Cephalometrics for you and me. Am J Orthod. 1953;39(10):729–755.