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Lips measurement

Burstone B-Line

The line from subnasale to the chin. Both lips should sit in front of it — the upper lip about 3.5 mm and the lower lip about 2.2 mm — with the lower lip behind the upper. A lower lip at or behind the line, or ahead of the upper lip, scores poorly.

SnPogLsLi
The points and construction lines on a reference profile, with the Frankfort horizontal level.

At a glance

Ideal
Upper +3.5 mm · Lower +2.2 mm
Unit
millimetres
Weight in the overall score
3
Area
Lips

How it is measured

Distance of Ls and Li from the Sn–Pog line (positive = in front)

  • 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.

A lower lip level with or ahead of the upper lip is always Tier 3 (rating capped at 4.0).

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.

Upper lip
TierRangeRating
T1 Ideal2.5–4.5 mm9.5–10
T2 Acceptable0.5–2.5 mm or 4.5–6.5 mm4.3–9.5
T3 Poor< 0.5 mm or > 6.5 mm0–4.3
Lower lip
TierRangeRating
T1 Ideal1.2–3.2 mm9.5–10
T2 Acceptable0.0–1.2 mm or 3.2–5.2 mm4.3–9.5
T3 Poor< 0.0 mm or > 5.2 mm0–4.3

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 (Assumed equal to the S-line difference; the study did not report Sn–Pog distances.).
  • African descent: upper lip +4 mm; lower lip +4 mm (Assumed equal to the E-line difference.).
  • Middle Eastern: upper lip men +1.5 mm, women ±0 mm; lower lip men +1.5 mm, women ±0 mm.

Individual faces vary far more within any group than between groups; these are averages, not targets.

Related measurements

References

  1. Burstone CJ. The integumental profile. Am J Orthod. 1958;44(1):1–25.
  2. Legan HL, Burstone CJ. Soft tissue cephalometric analysis for orthognathic surgery. J Oral Surg. 1980;38(10):744–751.