Proportion

Profile proportion analysis steps back from any single landmark and looks at the overall shape of the face in profile: is it straight, convex (receding chin and/or forehead), or concave (prominent chin and/or forehead)? This single, holistic judgment is often the first impression a clinician forms of a patient's skeletal pattern, before any individual measurement is taken.

Proportion also covers whether the vertical thirds of the face (upper, middle, lower) are balanced with one another. Together, overall convexity/concavity and vertical proportion give a fast, high-level summary of facial harmony that frames how every other profile finding (upper profile, midface, lower face, lips) should be interpreted.

What It Evaluates

The clinician draws lines connecting three key points on the lateral photo — glabella, subnasale, and pogonion — and measures the angle they form to classify the profile as straight, convex, or concave. Separately, the vertical distances between the hairline, glabella, subnasale, and chin are compared to check whether the upper, middle, and lower facial thirds are proportionate to one another.

Learn more: Facial Convexity Angle: How It's Measured & What Shapes Your Profile — Qoves Studio

Key References / Landmarks

  • Facial convexity angle (glabella–subnasale–pogonion) — the angle formed at subnasale between lines drawn to glabella and to pogonion; a commonly cited normal range is 165°–175°. Values within this range indicate a straight profile; a convex profile (associated with a Class II skeletal tendency) shows the chin sitting further back relative to this line, while a concave profile (associated with a Class III tendency) shows the chin projecting further forward.
  • Straight profile — forehead, lips, and chin fall in a relatively balanced vertical alignment; generally regarded as the most esthetically neutral profile type and often associated with a Class I skeletal/dental relationship.
  • Convex profile — a rounded, outward-curving profile with a receding chin (and/or prominent upper lip/maxilla); frequently linked to Class II skeletal patterns.
  • Concave profile — an inward-curving profile with a prominent chin and/or forehead relative to the midface; frequently linked to Class III skeletal patterns.
  • Facial thirds (trichion–glabella–subnasale–menton) — the face is divided into upper (trichion to glabella), middle (glabella to subnasale), and lower (subnasale to menton) vertical segments; the classical esthetic target is near-equal thirds, though real, esthetically acceptable faces commonly show some natural variation, with the lower third being the segment most relevant to orthodontic and orthognathic treatment planning.

Learn more: Facial Proportions — Plastic Surgery Key

Clinical Interpretation

The convexity/concavity classification gives the orthodontist a quick, whole-face read on the underlying skeletal (Class I/II/III) relationship before diving into cephalometric detail, and it is one of the main patient-facing ways to explain why a certain treatment approach (growth modification, extraction, surgery) is being recommended. Because this angle summarizes glabella, subnasale, and pogonion together, an abnormal reading should always be cross-checked against the individual upper-profile, midface, and lower-face findings to determine whether the imbalance originates from the forehead/nose, the maxilla, or the mandible/chin — since very different treatment strategies follow from each. Vertical thirds proportion is used the same way: a disproportionately long or short lower third often reframes what would otherwise look like a purely dental problem into one that also involves vertical jaw relationships, which can change the entire treatment plan.

Learn more: Determining Skeletal Class II and III — YouTube

References