Steiner Analysis in Cephalometrics: Measurements, Norms and Chevrons

The Steiner analysis remains one of the most widely taught cephalometric analyses in orthodontics. It is short, easy to read, and in a few measurements it gives a picture of the skeletal discrepancy and of the incisor position. This guide covers its landmarks, its reference planes, its norms and, above all, its limits, then the planning part that is often skipped: Steiner’s chevrons and incisor repositioning. The goal is to use it with judgment, not as a verdict.

The principles of the Steiner analysis

Cecil C. Steiner proposed his analysis in the early 1950s. From the analyses of his time, he selected the measurements he found most useful clinically, and the result fits on a single sheet.

The analysis rests on a simple idea: the anterior cranial base, represented by the S-N line, is the reference. The maxilla, the mandible and the incisors are located relative to it.

It has three components:

• the skeleton: sagittal position of the jaws and divergence;
• the teeth: inclination and position of the upper and lower incisors;
• the soft tissues: position of the lips relative to Steiner’s S line.

It also has three stages. The diagnostic stage describes the case; the prognostic stage, with the chevrons, sets the incisor position to aim for; the therapeutic stage, with the Steiner box, checks whether that position fits in the mandibular arch.

Landmarks and reference planes

The cephalometric landmarks

The tracing starts by identifying the landmarks on the lateral cephalogram. Their precision determines every measurement that follows. Our cephalometric tracing guide details the pitfalls of each one.

Add the incisal edges and apices of the incisors, the most labial points of their crowns for the millimeter measurements, and the soft-tissue points needed for the S line (columella of the nose and soft-tissue pogonion).

The reference planes

The landmarks define a few lines and planes:

• S-N: the cranial base reference line;
• N-A and N-B: the lines that locate each jaw and also serve as references for the incisors;
• Go-Gn: the mandibular plane chosen by Steiner;
• the occlusal plane: through the overlap of the molars and premolars; Steiner relates it to S-N (about 14°).

The choice of Go-Gn as the mandibular plane is specific to Steiner. Other analyses, such as Tweed’s, use a mandibular plane tangent to the lower border of the mandible. The values are therefore not directly comparable from one analysis to another.

Steiner’s measurements and norms

Skeletal measurements

• SNA: locates the maxilla relative to the cranial base.
• SNB: locates the mandible relative to the cranial base.
• ANB: the difference SNA − SNB; it expresses the sagittal discrepancy between the jaws.
• SN-GoGn: the angle between the cranial base and the mandibular plane; it describes facial divergence.

Dental measurements

• U1-NA in degrees: inclination of the upper incisor relative to N-A.
• U1-NA in millimeters: distance from the most labial point of the crown to the N-A line.
• L1-NB in degrees: inclination of the lower incisor relative to N-B.
• L1-NB in millimeters: distance from the most labial point of the crown to the N-B line.
• Interincisal angle: the angle between the long axes of the two incisors.

The norms

These are the norms used by our free cephalometric analysis tool, taken from university course handouts. Standard deviations vary between sources and populations. These norms were established on samples of North American origin: applying them to another population calls for caution.

Interpreting the results

Read the diagnostic stage in order: sagittal skeletal (SNA, SNB, ANB), vertical skeletal (SN-GoGn, occlusal plane to S-N), dentoskeletal (U1-NA, L1-NB, Pog-NB), dental (interincisal angle), and finally esthetics (lips relative to the S line).

The skeletal discrepancy

ANB is the most quoted measurement. The usual guidelines, with cut-offs that vary slightly between authors:

• ANB close to 2°: skeletal Class I relationship;
• ANB clearly above 4°: tendency toward a skeletal Class II;
• ANB zero or negative: tendency toward a skeletal Class III.

SNA and SNB tell you where the discrepancy comes from. A high ANB can come from a forward maxilla, a retruded mandible, or both, and the treatment approach is not the same.

Divergence

A high SN-GoGn points to a hyperdivergent pattern, a low value to a hypodivergent pattern. This reading is usefully cross-checked with the FMA of the Tweed analysis, described in our Tweed article (in French).

The incisor position

The dental measurements show whether the incisors are protruded, retruded or well placed on their bony base. One rule avoids many mistakes: speak of dentoalveolar protrusion only when the angle and the distance of the incisor are both increased (retrusion when both are decreased). An increased angle alone describes labial tipping.

These measurements also reveal dentoalveolar compensations: in a skeletal Class II, the lower incisor is often proclined; in a Class III, it is often retroclined.

The limits of ANB, and the Wits appraisal

ANB is convenient, but it is not reliable in every situation. Several factors change it without any real change in the relationship between the jaws:

• the position of N: a Nasion located further forward or further back than average changes ANB;
• the inclination of S-N: a more or less inclined cranial base distorts SNA and SNB;
• jaw rotation: a clockwise rotation tends to increase ANB, a counterclockwise rotation to decrease it;
• facial height: the farther A and B are from N, the more the same linear discrepancy translates into a different angle.

This is why ANB is often supplemented by the Wits appraisal, described by Jacobson in 1975. The Wits is not part of the Steiner analysis. Points A and B are projected perpendicularly onto the functional occlusal plane, and the distance between the projections (AO and BO) is measured.

Reference values differ between traditions: Steiner course materials give 0 ± 2 mm, Tweed sheets 2 ± 2 mm, and values close to 0 mm in women and about −1 mm in men are also quoted. Always state which norm you use. The Wits has its own weaknesses: it depends directly on how the occlusal plane is traced, which can be hard to define in the mixed dentition or with a deep curve of Spee.

A classic teaching example: an ANB of 4° (upper limit) with a Wits of −1 mm remains a borderline Class I, not a Class II. When ANB and the Wits disagree, no single number decides. The clinical examination of the profile, the incisor position and the other analyses take over.

Steiner’s chevrons: from diagnosis to treatment goal

Steiner did not stop at diagnosis. He proposed a planning method based on one observation: in a patient whose ANB will not be normalized, aiming for the average incisor values is not always realistic. The incisors can compensate for a moderate skeletal discrepancy.

Each step of the reasoning is summarized by a chevron: a V pointing to the right, with ANB at the top, U1-NA and L1-NB (in millimeters) on its arms and Pog-NB, the chin prominence, at the bottom.

1. Chevron 1, the problem: the patient’s initial measurements.
2. Chevron 2, the compromise: estimate the end-of-treatment ANB, then read the incisor position that Steiner considers acceptable for that ANB.
3. Chevron 3, esthetics: according to Holdaway, the lower incisor lines up with the chin (L1-NB = final Pog-NB, growth included).
4. Chevron 4, the solution: the average of chevrons 2 and 3, which reconciles function and esthetics.
5. Chevron 5, individualized: if space is still lacking after balancing the Steiner box.

Estimating the final ANB

In a growing child, under favorable conditions (remaining growth, anterior rotation, possible orthopedic treatment, good cooperation), the end-of-treatment ANB is often estimated at initial ANB / 2 + 1. If these conditions are lacking, the estimate is weighted downward. In adults, orthodontics alone does not change ANB: the initial ANB is kept.

Steiner’s acceptable compromises

For each degree of ANB above 2°, the upper incisor moves back by 1° and 1 mm and the lower incisor moves forward by 1° and 0.25 mm. The table is only defined between −1° and 8°: beyond this range, dental compensation alone is no longer enough and skeletal correction should be discussed.

Equivalent formulas: U1-NA (°) = 24 − ANB; U1-NA (mm) = 6 − ANB; L1-NB (°) = 23 + ANB; L1-NB (mm) = 3.5 + 0.25 × ANB.

The Holdaway ratio and chin growth

Holdaway relates the position of the lower incisor to the prominence of the chin: ideally, L1-NB equals Pog-NB. A difference of 1 to 2 mm remains esthetic, 3 mm is barely acceptable, and from 4 mm in favor of the incisor, uprighting it becomes essential for the profile.

Chevron 3 uses the end-of-treatment Pog-NB, so chin growth must be estimated. The usual guideline over 2 years of treatment is about +1 mm of Pog-NB in girls and +2 mm in boys, more with an anterior rotation or if the initial Pog-NB is already large, and no growth in adults.

Two precautions apply. The chevron values differ between reproductions and editions: refer to the source used in your program. And these compromises were designed for a given era and population. They guide the reasoning; they do not replace the examination of the periodontium, the profile and the soft tissues.

Incisor repositioning and the Steiner box

Incisor repositioning (IR) converts the movement of the lower incisor into millimeters of arch length: IR = (final L1-NB − initial L1-NB) × 2, because both sides of the arch are involved. In the Steiner box, it is added to crowding and to the curve of Spee to assess the space required and decide on possible extractions. The box is filled line by line in our Steiner box guide (in French), and crowding can be measured from an occlusal photo with our free space analysis tool.

The limits of the Steiner analysis

Steiner has known weaknesses. Its reference points are periosteal, so they remodel; it does not measure posterior crowding; and it ignores the influence of the vertical dimension on the position of the lower incisor. This is why it is usefully completed by the Tweed analysis, which ties the lower incisor target to the divergence (FMA).

In practice: a checklist

Before commenting on a Steiner analysis, check the following:

1. The lateral cephalogram is of good quality, taken in occlusion, with the head correctly oriented.
2. Landmarks S, N, A and B are placed carefully, especially A and B, which are often low in contrast.
3. The mandibular plane used is Go-Gn, not another plane.
4. ANB is checked against the Wits and the clinical examination of the profile.
5. The dental measurements are read with the skeletal discrepancy in mind.
6. The norms are adapted, as far as possible, to the patient’s population.

If the landmarks were placed by automatic software, checking them remains essential. Our article on artificial intelligence in cephalometrics (in French) lists the landmarks most often misplaced.

Frequently asked questions

What does ANB mean in the Steiner analysis?

ANB is the angle between the N-A and N-B lines, equal to SNA − SNB. It expresses the sagittal discrepancy between the maxilla and the mandible. Its norm is 2° ± 2°: above 4° suggests a skeletal Class II, below 0° a skeletal Class III. Because it depends on Nasion, the S-N inclination and jaw rotation, it should be confirmed with the Wits appraisal.

What are the normal values of the Steiner analysis?

SNA 82° ± 2°, SNB 80° ± 2°, ANB 2° ± 2°, SN-GoGn 32° ± 5°, U1-NA 22° ± 2° and 4 mm ± 1, L1-NB 25° ± 2° and 4 mm ± 1, interincisal angle 131° ± 5°. Standard deviations vary between sources, and the norms come from North American samples.

Why measure U1-NA and L1-NB in both degrees and millimeters?

The angle describes the inclination of the incisor, the distance its position. A tooth can be tipped without being displaced, or displaced bodily without being tipped. Only when both values are increased together can you speak of dentoalveolar protrusion. The millimeter values require a calibrated radiograph.

Steiner or Tweed: which analysis should I use?

They complement each other. Steiner focuses on the sagittal discrepancy and the incisor position relative to the cranial base; Tweed on the divergence and the lower incisor relative to the Frankfort and mandibular planes. Do not mix their planes or their norms: the mandibular plane and the occlusal plane are not the same in the two analyses.

Can I calculate Steiner’s chevrons online?

Yes. Our free Steiner’s chevrons calculator builds the four chevrons and the incisor repositioning from ANB, U1-NA, L1-NB and Pog-NB, with every formula explained. If you do not have the measurements yet, our cephalometric analysis tool calculates them from the landmarks you place on the radiograph.

With GS Ortho

In GS Ortho, AI places 29 landmarks on the lateral cephalogram and the Steiner analysis is calculated straight away, alongside Tweed. You check each landmark, correct it if needed, then validate: the decision stays yours. The measurements feed into the diagnostic studio, the Steiner box carries the incisor repositioning into the patient’s space analysis, and an orthodontist’s opinion can be requested in one click, straight from the panel. The GS Ortho interface is currently available in French.

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