Neutral Proportions

Neutral Proportions is a frontal-view facial esthetic analysis performed on a photograph of the patient's face at rest, without smiling or speaking. It measures how the face divides vertically into thirds and horizontally into fifths, comparing the patient's proportions against long-established anthropometric norms used in orthodontics, oral and maxillofacial surgery, and facial plastic surgery.

These proportions matter in orthodontic diagnosis because the position of the teeth and jaws directly shapes the lower third of the face. A patient can have perfectly aligned teeth and still look unbalanced if the underlying facial thirds or fifths are disproportionate, and conversely, understanding these proportions helps the clinician decide whether a case needs orthodontics alone or a combined orthodontic-surgical approach to restore facial harmony.

What It Evaluates

On the frontal photograph, the analysis places four vertical landmarks along the midline of the face — the trichion (hairline), glabella (the smooth prominence between the eyebrows), subnasale (the point where the nasal septum meets the upper lip), and menton (the lowest point of the chin) — and evaluates whether the three resulting segments (upper, middle, and lower facial thirds) are roughly equal in height.

At the same time, the analysis evaluates the width of the face in five horizontal segments, using the width of one eye (measured between the medial and lateral canthus) as the basic unit. In a well-proportioned face, each eye occupies one fifth of the total facial width, the space between the eyes (the intercanthal distance) is equal to the width of one eye, and the two outer fifths (from the lateral corner of each eye to the corresponding ear) are also roughly equal to that same unit. The intercanthal width is also expected to closely match the width of the nasal base (the alar width).

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Key References / Landmarks

Trichion (Tr) – Glabella (Gl) — the upper facial third, spanning the forehead from the hairline to the brow ridge; less clinically actionable than the other two thirds because the hairline can recede or vary independently of the skeleton.
Glabella (Gl) – Subnasale (Sn) — the middle facial third, spanning the midface from the brow ridge to the base of the nose; reflects the vertical development of the nasomaxillary complex.
Subnasale (Sn) – Menton (Me) — the lower facial third, spanning from the base of the nose to the bottom of the chin; the segment most influenced by dental and skeletal orthodontic factors, including maxillary and mandibular vertical position and incisor display.
Ideal vertical ratio — in a balanced face the three thirds (Tr-Gl, Gl-Sn, Sn-Me) are approximately equal in height (roughly 1:1:1); the lower third itself is commonly subdivided into an upper portion (subnasale to the lower lip / stomion) and a lower portion (stomion to menton) with an expected ratio near 1:2.
Horizontal fifths — the facial width divided into five equal units based on eye width: the two lateral fifths (ear to outer canthus), the two eye-width fifths (outer to inner canthus of each eye), and the central fifth (intercanthal distance, inner canthus to inner canthus).
Intercanthal width vs. alar width — the distance between the inner corners of the eyes is expected to approximate the width of the nasal base; a mismatch flags a transverse discrepancy worth investigating further.

Learn more: Transverse Facial and Dental Proportions - About Braces

Clinical Interpretation

Because the lower facial third is the segment most affected by orthodontic and orthognathic treatment, it receives the most clinical attention. A lower third that is visibly taller than the middle third can point toward increased anterior lower face height, vertical maxillary excess, or a skeletal open-bite (long-face) tendency, and often correlates with lip incompetence and excessive gingival display on smiling. A shortened lower third, by contrast, is often seen in deep-bite, short-face patterns, where the chin appears to sit close to the nose.

Horizontal fifths help the clinician screen for transverse and asymmetry problems: a central fifth that is narrower or wider than the eye-width fifths can suggest orbital or nasal width anomalies rather than a dental issue, while uneven lateral fifths can be an early sign of facial asymmetry that later needs to be confirmed with a full frontal symmetry analysis and, if needed, imaging.

None of these measurements are used in isolation. Deviations from ideal thirds or fifths are cross-checked against the patient's profile analysis, smile analysis, and cephalometric values before any treatment decision — such as extraction versus non-extraction, or orthodontics alone versus a combined surgical-orthodontic plan — is made. The value of Neutral Proportions is that it gives the clinician an early, photograph-based screening of overall facial balance before more detailed diagnostic records are taken.

Learn more: Evaluating Facial Esthetics: Vertical Proportion - Spear Education