Lips · Side photo

Lower lip to B-line

Burstone line

Burstone's line, checked for the lower lip.

How it's measured

Distance of the most forward point of the lower lip (labrale inferius) from the line from the base of the nose (subnasale) to the chin (pogonion), as a percentage of face height (nasion to menton). Positive means in front of the line, negative behind it. One decimal, because 1% is only about 1.2 mm.

Reference range

Male reference

0.8–2.8%

Female reference

0.9–3.0%

Source: Burstone 1967 (Am J Orthod 53:262-284): lower lip on average 2.2 mm in front of the line, as in the community formula's top range. Range 1-3.5 mm in front, converted to % of face height.

In the score

Counts toward the score with weight 2.5 (Community formula point table: Burstone line, 5 points, split evenly between the two lips).

What changes it

• Typical values differ between populations, so the reference range fits some faces better than others.
• Measured on the skin outline, so muscle and soft tissue affect it as well as bone.

One number, one feature

One measurement describes one detail in one photo. Pose, lens and expression move it, and every reference range is an average from limited samples.