Nasolabial Angle: Definition, Norms and How to Measure
The nasolabial angle is one of the few soft tissue measurements that every orthodontic examination records. It describes how the upper lip meets the base of the nose, and it is often quoted when extractions or incisor retraction are discussed. It is also easy to misread: half of the angle belongs to the nose, which orthodontics does not move, and the "normal" value depends on the source and on the patient’s sex. This guide covers how the angle is defined and measured, which norms our course materials give, what changes it, what the evidence says about extractions, and how it relates to the E-line and to Holdaway’s analysis.
What the nasolabial angle is
The nasolabial angle is formed at subnasale, the point where the columella merges with the upper lip, between two lines:
- a line tangent to the columella, the lower border of the nose;
- a line tangent to the upper lip, running down toward labrale superius, the most anterior point of the upper lip.
A large value means an open angle (upper lip inclined backward, or nose tip turned up); a small value means a closed or acute angle (upper lip inclined forward, or nose tip drooping).
Boileau, cited in our D.U. knowledge base, asks for the angle to be read in two parts: the columella component, which is out of the orthodontist’s reach, and the lip component, which is linked to the incisors. The same text gives the expected orientation of the upper lip: downward and forward, at worst vertical (perpendicular to the Frankfort plane); a lip inclined backward is a finding in itself.
How to measure the nasolabial angle
On a profile photo
- Use a standardized right profile: Frankfort plane horizontal, teeth in occlusion without strain, lips at rest, nothing hiding the base of the nose. Our French orthodontic photo protocol lists the common errors.
- Mark the columella (its lower border, under the nose tip), subnasale and the upper lip.
- Draw the columella tangent and the upper lip tangent through subnasale, then read the angle between them.
An angle is independent of image scale, so a photo needs no ruler for this measurement, unlike millimeter distances. It does depend on head posture and on the camera axis: a head tipped back opens the apparent angle, and a lens too close distorts the nose.
On a lateral cephalogram
The same construction applies to the soft tissue profile of the radiograph, provided the profile has enough contrast and the lips were at rest. Our cephalometric tracing guide covers these conditions. Strained lips closing over proclined incisors change the lip tangent and the reading.
One angle, several constructions
Some protocols use tangents, others use points: for example, the most anterior point of the columella, subnasale and the most anterior point of the upper lip. The two constructions do not give exactly the same number, and the columella tangent is the most operator-dependent part. Name the construction when you report a value, and keep the same one on follow-up records.
Nasolabial angle norms
Values from our course materials
Our knowledge base does not give a single norm. It reports these values and leaves the question open:
| Source (as cited in the base) | Females | Males |
|---|---|---|
| D.U. clinical examination course | 100-110° | 90-100° |
| S6 course | 85-105° (not split by sex) | 85-105° |
| Boileau | 100-110° | 90-95° |
| Literature (Legan and Burstone) | 102 ± 8° (90-110°), not split by sex | same |
The D.U. value by sex is the one retained by default in our clinical rules. Boileau agrees with it for girls and gives a narrower range for boys. Whatever value you use, say which one.
The norm is also a population average. Boileau, cited in our base, considers norms specific to each ethnic group indispensable for cephalometrics in general; we did not find in PubMed nasolabial norms drawn from Maghreb samples that we could cite here.
Open, normal or closed
In practice the angle is recorded as normal, open or closed against the chosen norm, and interpreted with the rest of the profile:
- a closed angle with lips ahead of the esthetic lines, lips apart at rest and a marked labiomental fold suggests bimaxillary dentoalveolar protrusion; Boileau describes it with a convex subnasal profile, thick soft tissues and thin, proclined alveolar processes;
- an over-open angle belongs to the "profile at risk" described in the courses (projected midface, short chin-throat distance, prominent nose or chin, thin lips, marked labiomental fold, short face), where extractions and anchorage must protect the profile;
- in Class III, the base reports a disagreement: "often open" in one course and in the EMC, closed with a small nose in Boileau. Both are possible depending on the maxillary component and the compensation of the upper incisors, so the angle has to be measured, not presumed.
What changes the nasolabial angle
Incisor position and retraction
The lip component follows the upper incisors. Retracting them, by extractions, distalization or headgear, tends to move the upper lip back and open the angle. The course materials name several situations:
- in Class II, the upper lip moves back as the overjet is corrected, especially when the upper arch is distalized, and the angle opens; the risk is greater with a columella already oriented upward (Boileau);
- headgear on a splint moves the whole upper arch back and can open the angle;
- low-pull headgear in a hyperdivergent patient extrudes the upper molars, rotates the mandible backward and opens the angle (Merrifield and Cross, cited by Boileau);
- among the factors that individualize the incisor target, Boileau lists the effect of upper incisor retraction on the nasolabial angle.
How much the lips follow the incisors is itself debated; the base keeps several ratios side by side, from about 1 mm of upper lip retraction per 2 mm of incisor retraction in the D.U. course to 1/1.75 to 1/2.2 in the Leonardi review cited by Boileau. After retraction, the change in the nasolabial angle varies with the facial type.
Growth and aging
In adults, the base describes a nose that droops and widens, lips that thin and move back, and a nasolabial angle that closes with age. It calls for caution before accentuating a retraction in an adult profile.
Functional appliances and surgery
For activators, the courses describe the nasolabial angle as little changed. A meta-analysis of functional treatment found it opened by about 5.8° after Twin-block treatment compared with controls, from three studies with low-quality evidence (Almrayati et al., 2024, Cureus). In orthognathic surgery, the base notes that a Le Fort I advancement moves the upper lip forward, opens the nasolabial angle and lifts the nose tip while widening the alar base.
The extraction debate: what the evidence shows
Whether premolar extractions "flatten" the profile is an old argument. The meta-analyses point the same way, with weak evidence:
- Extraction vs non-extraction: extraction treatment was associated with a larger nasolabial angle (21 studies, 1,089 patients, mean difference 4.21°), more retraction of both lips and a more pleasant profile on average; patient age, extraction protocol and the amount of upper incisor retraction influenced the effect. The quality of evidence was very low, and the authors conclude that no consistent prediction of profile response can be made (Konstantonis et al., 2018, Eur J Oral Sci).
- Adults: in five studies of moderate quality, extraction protocols were associated with lip retraction and an increase in the nasolabial angle; whether this helps or harms the profile depends on other factors (Almurtadha et al., 2018, J Evid Based Dent Pract).
- Class II division 1: the angle increased by 2.4 to 5.4° with two-premolar extraction protocols and by 1 to 6.84° with four-premolar protocols, with less lower lip retraction in the two-premolar groups (Janson et al., 2016, Eur J Orthod).
- Non-growing patients with bimaxillary protrusion: after four-premolar extractions, the upper lip moved back by 2 to 3.2 mm and the lower lip by 2 to 4.5 mm, and the angle increased; the authors describe the changes as small, not a "dished-in" profile, with large individual variation (Leonardi et al., 2010, Angle Orthod).
- Anchorage: with mini-implant anchorage, the angle increased by about 4.7° more than with two-step retraction on conventional anchorage (Khlef et al., 2018, Contemp Clin Dent).
The reading that fits both the evidence and the course materials: extractions do not flatten every profile, and they do not leave it untouched either. What changes the nasolabial angle is the amount of incisor retraction, and that depends on the anchorage, the starting position of the incisors and the patient’s soft tissue. Our French article on extraction criteria sets out the decision criteria; a closed angle with protrusive incisors and a straight or open angle with a prominent nose are two very different starting points.
Nasolabial angle, E-line and Holdaway
The nasolabial angle rarely decides anything on its own. It is read alongside the lip lines and the hard tissue measurements:
- Ricketts’ E-line runs from the nose tip to soft tissue pogonion. Like the nasolabial angle, it depends on the nose: a large nose makes normal lips look retruded, and a closed angle can come with lips that sit well relative to the line. Our article on the Ricketts E-line gives its norms and limits, and our French article compares it with Steiner’s S line.
- The Holdaway ratio compares the lower incisor (L1-NB) with the bony chin (Pog-NB) on the cephalogram. It tells you whether the incisor is in balance with the chin, which the nasolabial angle cannot: see our article on the Holdaway ratio.
- Incisor angles (U1-NA, U1-SN) tell you whether the lip component of the angle comes from proclined or upright incisors. Our free cephalometric analysis tool calculates the Steiner and Tweed incisor measurements; it has no soft tissue landmarks, so it does not compute the nasolabial angle.
A useful habit is to explain an abnormal angle by its two components: is it the columella (nose tip up or down), or the lip (incisors forward or back, thick or thin lip)? Only the second can be changed by tooth movement.
In practice: a checklist
- Record the angle on a standardized profile photo or cephalogram, lips at rest, head in natural or Frankfort position.
- State the construction (tangents or points) and the norm used, with its source and the patient’s sex.
- Split the reading into columella and lip components; check the upper lip orientation.
- Cross-check with the E-line or S line, the incisor angles and the Holdaway ratio.
- Before retracting upper incisors, estimate how much the angle may open, especially with an upturned columella, thin lips or an adult profile.
- Treat the angle as one criterion in the extraction and anchorage decision, never as the decision.
Frequently asked questions
What is a normal nasolabial angle?
It depends on the source and on sex. Our course materials give 100-110° for females and 90-100° for males; Boileau gives 90-95° for males; another course gives 85-105°, and the literature value usually quoted is 102 ± 8° (Legan and Burstone). No single number fits every patient.
What does an obtuse (open) nasolabial angle mean?
The upper lip is inclined backward, the nose tip is turned up, or both. It can come with retruded upper incisors, a thin upper lip or the soft tissue changes of a large incisor retraction. Whether it needs any change depends on the whole profile, which only an orthodontist’s examination can assess.
Can braces change the nasolabial angle?
Yes, through the lip component. Retracting the upper incisors tends to open the angle; meta-analyses report a mean increase of about 4° with extraction treatment, with wide variation between patients (Konstantonis et al., 2018). The columella component does not change with orthodontic treatment.
Do extractions always ruin the profile?
No. Reviews show lip retraction and an opening of the nasolabial angle on average, but the changes are usually small and vary greatly between patients (Leonardi et al., 2010; Konstantonis et al., 2018). The risk is real in a straight or already flat profile, which is why the courses ask to protect "profiles at risk".
With GS Ortho
In GS Ortho, the diagnostic studio guides the case through 12 panels; the clinical examination panel records the nasolabial angle as normal, open or closed, alongside each lip against Steiner’s S line, next to the photos and the cephalometric analysis of the same patient. AI places 29 landmarks on the lateral cephalogram for you to check and correct before the Steiner and Tweed analyses are calculated. You validate each step: the decision stays yours. The GS Ortho interface is currently available in French.