Lips

Lip analysis looks at how far forward or backward the upper and lower lips sit relative to a set of standardized reference lines drawn across the profile photograph. Because lip position is heavily influenced by the position of the incisors behind them, this is one of the most direct links between tooth movement and how a patient's profile is perceived.

Several esthetic lines have been proposed over the decades — Ricketts' E-line and Steiner's S-line are the two most widely used in day-to-day orthodontic diagnosis — and each gives a slightly different "ideal" answer, so orthodontists typically consider more than one line together with lip competence and thickness rather than relying on a single number.

What It Evaluates

The clinician measures how far the most prominent point of the upper lip and lower lip sit in front of, on, or behind a reference line drawn from the nose to the chin. This is combined with an assessment of lip competence — whether the lips can close together at rest without strain — and the relative balance between the upper and lower lip.

Learn more: What Is Lip Incompetence (Mentalis Strain)?

Key References / Landmarks

  • Ricketts' E-line (esthetic line) — drawn from the tip of the nose (pronasale) to the soft-tissue chin (pogonion); in a harmonious profile the lower lip sits about 2 mm behind this line and the upper lip about 3–4 mm behind it. Lips falling in front of the line suggest a protrusive profile; lips well behind it suggest a retrusive one.
  • Steiner's S-line — drawn from the soft-tissue pogonion to the midpoint of the "S" curve formed by subnasale and the tip of the nose; for a balanced profile, both lips should just touch this line, with more anterior placement read as protrusive and more posterior placement as retrusive.
  • Burstone's line (B-line) — an additional soft-tissue reference line used alongside the E-line and S-line in some sagittal lip-position analyses to cross-check protrusion/retrusion findings.
  • Labrale superius (Ls) / Labrale inferius (Li) — the most anterior points of the upper and lower lip vermillion border, used as the measurement points against each reference line.
  • Lip competence — the ability of the lips to seal passively at rest; incompetent lips (requiring muscular effort to close, or an open resting posture) are frequently associated with Class II division 1 malocclusion, increased overjet, or mouth breathing habits.

Learn more: Ricketts E-Line: How It's Measured & Why Orthodontists Care About It — Qoves Studio

Clinical Interpretation

Because upper and lower incisor position directly supports the lips, retracting or advancing the anterior teeth during treatment moves the lips along with them — which is why lip position relative to the E-line and S-line is checked both before treatment (to help decide between extraction and non-extraction options) and as a predicted outcome of the proposed tooth movements. A markedly protrusive lip position combined with incompetent lips often points toward a treatment plan that retracts the incisors to improve lip seal and profile balance, while an already retrusive or thin lip may caution against further retraction, since over-retracting can flatten the profile and make the patient appear older. Comparing results across more than one reference line (E-line and S-line together) helps avoid over-interpreting a single measurement, since normative values differ by sex, ethnicity, and the individual thickness of the lips.

Learn more: Extraction vs Non-Extraction Orthodontics: Who's Right and Who's Wrong? — Dr. Jamal Farhan (YouTube)

References