Soft tissue profile lines explained: E-line, S-line and Burstone’s line

Simplified Orthodontics Academy · Published 27 October 2026

Key points

A soft tissue profile line is a straight line drawn between two points on the profile. The distance of each lip from the line is measured in millimetres.
The E-line runs from the tip of the nose to the soft tissue chin. The S-line runs from the soft tissue chin to the middle of the S-shaped curve under the nose. Burstone’s line (B-line) runs from subnasale to the soft tissue chin.
The distance is measured at right angles to the line. In Simplified Face, a lip in front of the line has a positive value and a lip behind it a negative value.
One profile gives a different reading on each line, because each line passes through different points. Moving the nose tip changes the E-line reading but not the B-line reading.
Simplified Face measures both lips to the E-line and to Burstone’s line on a profile photograph. It does not draw the S-line.

What a soft tissue profile line is

A cephalometric analysis measures bones and teeth. A soft tissue profile line looks at the outline of the face instead: the nose, the lips and the chin, seen from the side. Each line is drawn through two soft tissue landmarks, points placed at defined sites on the profile [1]. The lips are then measured against the line.

Three things define every reading:

The two points that fix the line.
The point on the lip that is measured, usually its most forward point.
The direction of the distance and its sign: measured at right angles to the line, and positive or negative depending on the side of the line the lip lies on.

Change any one of the three and the number changes. So a reading can only be compared with reference values measured on the same line, from the same points, with the same sign. The lines can be drawn on the soft tissue outline of a lateral cephalogram or on a profile photograph. Simplified Face uses a profile photograph.

Figure 1. The three lines on one schematic profile, facing right. E-line: from pronasale (Prn) to soft tissue pogonion (Pog′). S-line: from Pog′ to the midpoint of the curve between subnasale (Sn) and Prn (open circle). B-line: from Sn to Pog′. A schematic outline made of simple curves, not a photo or a tracing of a person.

The soft tissue points

Prn, pronasale: the most forward point of the nose tip.
Sn, subnasale: where the columella, the lower border of the nose, meets the upper lip.
Ls, labrale superius: the most forward point of the upper lip.
Li, labrale inferius: the most forward point of the lower lip.
Pog′, soft tissue pogonion: the most forward point of the chin.

The prime (′) marks a soft tissue point and tells it apart from the bony point of the same name. “Most forward” depends on how the head is held, so the photograph must be taken with the head in a known position (see Taking the profile photograph). In Simplified Face, each landmark is shown with a short definition in these same terms.

The E-line (Ricketts)

Ricketts introduced the E-line, short for esthetic plane, in 1968 [2]. It is drawn from the tip of the nose (Prn) to the soft tissue chin (Pog′). The upper lip is measured to it from Ls, and the lower lip from Li.

Because the E-line passes through the nose tip, the nose changes the reading. A nose tip further forward moves the line forward, and both lips then read further behind it, although the lips have not moved. The worked example below shows this. Simplified Face labels the two readings “Upper lip to the E-line (Ricketts)” and “Lower lip to the E-line (Ricketts)”.

The S-line (Steiner)

The S-line, described by Steiner, runs from soft tissue pogonion to the midpoint of the S-shaped curve between subnasale and the tip of the nose (pronasale) [3]. The lips are measured to it in millimetres, as for the E-line.

Its upper point lies on the lower border of the nose, not at its tip. So the S-line depends less on how far the nose projects than the E-line does. It still moves when the shape of the nose changes, because the midpoint of the curve moves with it.

The S-line belongs to the soft tissue readings of Steiner’s cephalometric analysis; the Steiner analysis article covers it with his other readings. Simplified Face does not draw the S-line.

Burstone’s line (B-line)

Burstone studied the soft tissue profile, which he called the integumental profile, in 1958 [4]. The line from subnasale (Sn) to soft tissue pogonion (Pog′) comes from this work and is often called Burstone’s line or the B-line. The lips are measured to it from Ls and Li.

The B-line does not touch the nose tip. A change at the nose tip leaves the reading unchanged. A change at the chin moves all three lines, because all three end at Pog′. Simplified Face labels the two readings “Upper lip to Sn–Pog′ (Burstone)” and “Lower lip to Sn–Pog′ (Burstone)”.

Line	Upper point	Lower point	In Simplified Face
E-line	Prn	Pog′	Yes, both lips
S-line	Midpoint of the curve from Sn to Prn	Pog′	No
B-line	Sn	Pog′	Yes, both lips

How the lip distance is measured, and its sign

Draw the line through its two points.
From the lip point, Ls or Li, draw a perpendicular to the line.
Measure the length of the perpendicular in millimetres.
Give it a sign: one side of the line is positive and the other negative. In Simplified Face, the distance is positive when the lip lies in front of the line, on the side the face looks towards, and negative when the lip lies behind the line, on the side of the face.

The distance is taken at right angles to the line, not straight across in the horizontal direction. For a steep line the two differ only a little; the more the line leans, the larger the difference. The same method applies to the S-line and the B-line.

Check the sign convention before comparing a reading with a table. A lip 2 mm behind the line is −2 mm in Simplified Face. A source that reports distances without a sign would print 2 mm, and the reader has to know which side was meant.

A millimetre value also needs a calibrated photograph, one in which a known distance gives the scale. In Simplified Face, the photo is calibrated from one known distance, such as a ruler held at the face; without calibration the tool hides the millimetre values and shows only angles, ratios and percentages. To know which side of a line is the front, it uses the side the profile faces, which you set under Image.

Figure 2. Each lip is measured at right angles to the line. Both lips here lie behind the E-line, so both readings are negative: upper lip −6.4 mm, lower lip −4.0 mm, the starting values of the worked example. Schematic, enlarged.

Worked example

This example is a drawing, not a patient. We drew the schematic profile of Figure 1 on a millimetre grid, placed the six points, and measured both lips to each line with the method Simplified Face uses: the perpendicular distance, positive in front of the line. Then we moved one point at a time and measured again. Values are in millimetres.

Change	Upper lip to E-line	Lower lip to E-line	Upper lip to S-line	Lower lip to S-line	Upper lip to B-line	Lower lip to B-line
Starting drawing	−6.4	−4.0	−2.3	−1.6	+4.7	+2.6
Nose tip 3 mm further forward	−8.0	−5.0	−3.0	−2.0	+4.7	+2.6
Chin 3 mm further forward	−7.5	−5.9	−3.2	−3.3	+4.0	+1.0

On the same drawing, the upper lip is 6.4 mm behind the E-line, 2.3 mm behind the S-line and 4.7 mm in front of the B-line. Three lines give three numbers, and even the sign differs. A reading means something only next to the name of its line.
Moving the nose tip forward changed the E-line readings by 1.0 and 1.6 mm, and the S-line readings by less than 1 mm, because the midpoint of the curve moved too. The B-line readings did not change.
Moving the chin forward changed all six readings, because all three lines end at Pog′.

The lips never moved in this example. Every change came from a point that defines a line.

Taking the profile photograph

A photograph measures what the camera sees, so the way it is taken changes the numbers. Simplified Face asks for a profile in natural head position, with the patient looking at a distant point or a mirror at eye level, and the camera at eye height. The true vertical of the photo should stay vertical; a plumb line or a door frame behind the patient helps. A tilted photo can be levelled in the tool before the landmarks are placed.

The lips should be relaxed and in the same posture in every photo of the series. A lip that is pressed or pursed moves Ls and Li, and with them every reading on every line.

Limits

Landmarks are placed by eye. The most forward point of a rounded lip or chin can slide along the curve, and a small shift changes the reading.
Photograph or radiograph. The same line drawn on a photograph and on the soft tissue outline of a cephalogram need not give the same number: the image, its scale and the head position differ. Compare like with like.
Camera and calibration. A millimetre value is only as accurate as the calibration. A camera close to the face also enlarges the parts nearest to it.
Reference values come from particular samples. Simplified Face shows the published reference value next to each reading. These values come mainly from adult samples of European descent and may not suit every patient or population, so read them with the patient’s age, sex and background in mind.
Description, not decision. This article describes how the lines are drawn and measured. It does not cover what a reading means for diagnosis or treatment.

Do this in Simplified Face

Simplified Face measures the upper and lower lip to the E-line (Ricketts) and to the Sn–Pog′ line (Burstone) on a profile photograph, and shows each value next to its published reference value. You calibrate the photo, place the 12 profile landmarks, and the readings update as you work. All three views and every analysis are in the Free plan.

Open Simplified Face About Simplified Face

Educational content for clinicians and students. Reference values vary between populations. This page does not replace clinical judgement.

References

Jacobson A, Jacobson RL, eds. Radiographic Cephalometry: From Basics to 3-D Imaging. 2nd ed. Chicago: Quintessence; 2006. ISBN 978-0-86715-461-0.
Ricketts RM. Esthetics, environment, and the law of lip relation. Am J Orthod. 1968;54:272-289. doi: 10.1016/S0002-9416(68)90278-9
Singh AV, Mahamuni A, Gaharwar JS, Rai R, Yadav K, Sirishkusum C. Evaluation of change in the facial profile and aesthetics in relation to incisor position in both maxillary and mandibular arches. Cureus. 2023;15(1):e34403. doi: 10.7759/cureus.34403. PMID: 36874653
Burstone CJ. The integumental profile. Am J Orthod. 1958;44(1):1-25. doi: 10.1016/S0002-9416(58)90178-7