Ricketts E-Line: Lip Position, Norms and How to Measure

The Ricketts E-line, or esthetic line, is the quickest way to put a number on lip position in a profile: two points, one line, two distances. That simplicity is also its trap. The line depends on the nose and the chin as much as on the lips, and the "normal" distance depends on age, sex and population. Here is how to draw it, which norms to use, how it compares with the other soft-tissue lines, and what it tells you about incisors and extractions.

What the E-line is

The E-line runs from the tip of the nose (pronasale) to soft-tissue pogonion, the most anterior point of the soft-tissue chin. It was introduced by Ricketts to assess lip position; other reference lines (Steiner’s S line, Burstone’s B line, Holdaway’s H line) were proposed for the same purpose (Amirabadi et al., 2014, J Clin Exp Dent).

You then measure the shortest distance from the most anterior point of each lip to the line:

• a negative value means the lip lies behind the line;
• zero means it touches the line;
• a positive value means it lies ahead of the line.

This is the usual convention, but check it in any paper or software you compare with, and always write the sign: "2 mm" alone is ambiguous.

How to draw the E-line

On a lateral cephalogram

1. Check the radiograph: maximum intercuspation, head oriented on the Frankfort plane, lips at rest, enough contrast on the soft-tissue profile. Our cephalometric tracing guide details these conditions.
2. Trace the soft-tissue profile from the nose to below the chin.
3. Mark pronasale, the most anterior point of the nose, and soft-tissue pogonion.
4. Draw the line through the two points.
5. Mark the most anterior point of each lip and measure its perpendicular distance to the line, with its sign.

Millimeter values require a calibrated radiograph (the ruler on the film). A tracing left in pixels cannot be compared with any norm.

On a profile photo

Follow a standard protocol: right profile, Frankfort horizontal, hair tied back, tragus and chin-throat area visible, teeth in contact without strain. Photographing from too close enlarges the nose, which directly shifts the E-line; a tilted head or a false profile has the same effect. Our orthodontic photo protocol (in French) lists the common errors. Without a scale in the plane of the profile, describe the lips qualitatively (behind, on, ahead of the line) rather than in millimeters.

E-line norms: what the reference values say

Values from our course materials

Our D.U. knowledge base, which relies on Boileau and on the EMC resident’s manual for Ricketts’ values, does not give a single figure:

The two references do not agree on the lower lip, and the base does not settle the question. The EMC value is tied to age 9: it is not an adult target. Whichever value you use, state its source.

Age changes the "normal" value

In a longitudinal sample of 20 males and 15 females followed from 5 to 45 years of age, both lips became significantly more retruded relative to the E-line between 15 and 25 years, and the trend continued between 25 and 45. The greatest soft-tissue changes came earlier in females (10 to 15 years) than in males (15 to 25 years), and the authors note that they may influence the extraction decision in adolescents (Bishara et al., 1998, AJODO).

In our course materials, a teaching example follows one patient’s Z angle: 64° at 12 years, 70° at 12.9 years, 70° at 14.3 years, 69° at 21 years. The final profile has to be judged with the remaining growth in mind.

Population and sex

No single population’s value is universal. Boileau, cited in our base, considers norms specific to each ethnic group indispensable and lists the Maghreb population among those whose incisors are normally more proclined. Lips slightly ahead of a North American norm should not, on that basis alone, be read as a protrusion to correct. We found no E-line norms for Moroccan, Algerian or Tunisian samples in PubMed.

Studies elsewhere point in the same direction:

• In Saudi adults, males had more prominent and thicker lips than females, and lip prominence exceeded the norms (both lips in males, the lower lip in females) (Alshahrani et al., 2020, J Pak Med Assoc). Cross-sectional study; the abstract gives no sample size.
• Esthetic preferences vary too. Four panels of lay judges (European American, Hispanic American, Japanese, African) preferred mean lip positions between −2.13 and −3.45 mm from the E-line, and both judge and patient ethnicity and sex influenced the choice (Nomura et al., 2009, AJODO). The profiles were silhouettes.
• On African American adolescent profiles, orthodontic raters picked flatter profiles on silhouettes than on photos (Hockley et al., 2012, AJODO): judge lips on real photos.

The E-line and the other soft-tissue lines

Each analysis has its own esthetic line, and their norms are not interchangeable.

Steiner’s S line

The S line is the esthetic part of the Steiner analysis. Our course materials read it qualitatively: lips touching the line is normocheilia, ahead of it procheilia, behind it retrocheilia. Because it stops at the base of the nose instead of its tip, it is less influenced by nasal prominence than the E-line. In Chinese adults, S and E lines performed similarly at separating pleasing from unpleasing profiles, and the S line was judged more convenient chairside because its values sit closer to zero (Ng et al., 2023, AJODO).

Merrifield’s Z angle

Merrifield’s Z line is tangent to soft-tissue pogonion and to the most prominent lip, whichever it is; the Z angle is measured to the Frankfort plane. It belongs to the Tweed-Merrifield analysis described in our Tweed article (in French). A low Z angle means a protrusive or convex profile, a high one a flat profile. When the Z line is oblique, the course asks you to find out whether an advanced upper lip or a retruded chin is responsible.

Holdaway’s H line

Our course materials use Holdaway mainly for his ratio between lower incisor and chin (L1-NB compared with Pog-NB) and give no H line norm. In his own paper, Holdaway wrote that both lips and chin should line up near the H line and that the H angle must increase as skeletal convexity increases (Holdaway, 1984, Am J Orthod).

How to measure lip thickness

Lip position and lip thickness are two different things, and thickness explains much of the variation in position. The Tweed-Merrifield analysis taught in our D.U. measures, on the cephalogram:

• Upper lip thickness (UL): from the most prominent point of the upper lip to the labial surface of the upper central incisor;
• Total chin thickness (TC): from soft-tissue pogonion to its projection on the N-B line.

UL has no absolute norm; it is compared with TC, expected to be equal or larger (UL 11 mm and TC 15 mm in the course case).

Holdaway found the soft tissue at point A usually 14 to 16 mm thick in adolescents. A tapered upper lip in front of protrusive incisors first thickens as the incisors are retracted, and only then follows them about one to one; very thin or very thick tissues behave differently (Holdaway, 1983, Am J Orthod). Thickness also varies with sex and population: a Palestinian sample of 93 students with normal occlusion had thicker lips than Holdaway’s values (Hussein et al., 2011, Saudi Dent J).

What lip protrusion or retrusion means clinically

The link with incisor position

Our base describes bimaxillary dentoalveolar protrusion as increased incisor angles and distances, a very acute interincisal angle, lips ahead of the S and E lines and a very decreased Z angle; clinically, lips apart at rest, procheilia of both lips and a marked labiomental fold.

The reverse reading is not automatic. A lip can sit ahead of the line because the nose is small, the chin retruded or the lip thick, with well-placed incisors. Our course materials add a principle from Boileau (after Philippe): lip prominence is judged relative to the nose and the chin. The larger they are, the more protrusive the lips must be to balance the profile, so any lip target taken from the S, E or Z lines is modulated by nose and chin, and nose growth is estimated before setting the position of lips and incisors.

Extraction decisions: criteria, not rules

In the D.U., the esthetic line of the lips helps set the anterior limit of the dentition, that is, where the incisors may go. The course then gives criteria:

• Straight profile or "profile at risk" (prominent nose or chin, thin lips, marked labiomental fold): avoid extractions and limit incisor retraction.
• Very convex profile, bimaxillary protrusion: extractions can be considered.
• Bimaxillary protrusion in Class I: treating it is mainly an esthetic and cultural decision, shared with the patient and family; it becomes imperative when it prevents effortless lip closure (mentalis strain, mouth breathing, gingivitis) or strains a thin periodontium.
• Hypodivergent face: extractions are contraindicated in the D.U. (relatively, in Boileau); incisor retraction risks hollowing the subnasal profile.

How much the lips follow the incisors is itself debated; the base keeps three variants side by side:

Two warnings from the base: excessive incisor retraction flattens the profile when the target is misjudged: nose and chin growth underestimated, lip response that varies with tone and thickness, or naturally strong anchorage. And in borderline cases, the analyses (Tweed, Steiner, Ricketts, Merrifield) can disagree; the decision then rests on facial esthetics and the periodontium, not on one norm. Our article on extraction criteria (in French) details the reasoning.

The limits of the E-line

• The nose and chin grow. Both ends of the line move forward during adolescence, so the lips "retrude" relative to it without moving. In a meta-analysis of functional appliances, the lower lip appeared unchanged relative to the E-line after Twin-block treatment partly because the line itself shifted as pronasale and soft-tissue pogonion advanced; the upper lip moved back by about 1.9 mm compared with untreated controls, with very low certainty of evidence (Almrayati et al., 2024, Cureus).
• It depends on the nose. A large nose makes normal lips look retruded, a small nose the opposite. The S line is less sensitive to this.
• Lip posture. Strained lips closing over protrusive incisors, with mentalis contraction, hide their real position. Use lips at rest and note it.
• Aging. In adults, the lips thin and move back, the nose droops and the nasolabial angle closes. Our course materials call for caution before accentuating a retraction.
• Variable response to treatment. After upper first premolar extractions in 20 Class II division 1 patients, both lips moved back relative to the E-line, but by different amounts from patient to patient (Amirabadi et al., 2014). Over the long term, Boileau reports (after Stephens) that extractions do not change how the profile evolves.
• Norms come from specific samples, whose age, sex and population rarely match your patient’s.

In practice: a checklist

1. Use a calibrated cephalogram or a standardized profile photo, lips at rest, Frankfort horizontal.
2. Place pronasale and soft-tissue pogonion carefully, then measure both lips with their sign.
3. Name the norm you use, its source and the age it applies to.
4. Read the E-line with the nose, the chin, lip thickness (UL compared with TC) and lip competence.
5. Cross-check with the S line or the Z angle, and with the incisor measurements.
6. In a growing patient, factor in nose and chin growth, and treat the result as one criterion in the extraction decision, never as the decision.

Frequently asked questions

What is a normal E-line distance?

It depends on the source and on age. Our course materials cite Boileau’s values (upper lip −1 mm, lower lip 0 mm) and the EMC’s value for the lower lip at age 9 (−2 ± 2 mm). Lips normally move back relative to the line from adolescence into adulthood, and populations differ: no single number fits every patient.

What is the difference between the E-line and the S line?

The E-line goes from the nose tip to soft-tissue pogonion; Steiner’s S line goes from soft-tissue pogonion to the middle of the S-shaped curve at the base of the nose. Because it ignores the nose tip, the S line is less affected by nasal prominence, and lips normally just touch it. Their norms are not interchangeable.

Can orthodontic treatment change the E-line?

Treatment changes lip position relative to the line, mainly through incisor retraction or proclination, but the response varies with lip thickness and tone, and the line itself moves as the nose and chin grow. For a specific patient, only an orthodontist’s examination can say what change is realistic and desirable.

Is it the "Rickets" or the "Ricketts" line?

Ricketts, with two t’s: the line is named after the orthodontist who introduced it. Rickets is an unrelated bone disease.

Does the free GS Ortho tool calculate the E-line?

No. Our free cephalometric analysis tool calculates 12 Steiner and Tweed measurements (SNA, SNB, ANB, SN-GoGn, incisor angles and distances, interincisal angle, FMA, IMPA, FMIA). It has no soft-tissue landmarks, so it does not compute the E-line, S line or Z angle.

With GS Ortho

In GS Ortho, AI places 29 landmarks on the lateral cephalogram, soft-tissue profile included, and the Steiner and Tweed analyses are calculated straight away. The Tweed analysis includes Merrifield’s Z angle: the soft-tissue chin point is proposed automatically and you correct it if needed. The E-line itself is not calculated. In the diagnostic studio, the clinical examination records each lip against Steiner’s S line, and an orthodontist’s opinion can be requested in one click, straight from the case. You check, correct and validate: the decision stays yours. The GS Ortho interface is currently available in French.

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