Sassouni Analysis
The Sassouni Analysis (also called the Sassouni Archial Analysis) was developed in 1955 by Dr. Viken Sassouni at the University of Pittsburgh, based on a study of 100 Caucasian children aged 7–15. Instead of measuring skeletal relationships as a set of independent linear or angular values compared to a fixed statistical average, Sassouni introduced a geometric model of the face: he observed that in well-proportioned faces, several horizontal anatomic planes (drawn through different landmarks) tend to converge toward a single point, which he labeled point O.
Its clinical purpose is to judge facial and dental proportionality as a whole rather than tooth-by-tooth or angle-by-angle — making it especially useful for evaluating vertical growth pattern (long-face vs. short-face tendencies) and for anteroposterior (Class I/II/III) assessment in a single unified diagram. Modern digital adaptations (e.g., "Sassouni Plus") extend the original geometry with age-adjusted arcs and airway measurements.
What It Evaluates
The analysis constructs several horizontal reference planes — including the Frankfort Horizontal, the palatal plane, the occlusal plane, and the mandibular plane — and shows that in a proportionate face these planes, when extended posteriorly, tend to intersect near a common point O. From that point, Sassouni draws a series of concentric arcs (radii) out to key anatomical landmarks: an anterior arc to Nasion, an arc to ANS, an arc to Point A, a midfacial arc to Temporale, and a posterior arc to the posterior wall of Sella. Comparing how far each landmark sits from its expected arc — rather than reading raw angles against a population mean — reveals whether the face is vertically balanced (normodivergent), long and vertically excessive (retrognathic/hyperdivergent, arcs diverging), or short and vertically deficient (prognathic/hypodivergent, arcs converging).
Learn more: Sassouni Analysis (CephX)
Key Measurements
- Point O convergence — The degree to which the Frankfort Horizontal, palatal, occlusal, and mandibular planes converge toward a single posterior point; strong convergence indicates a proportionate, normodivergent vertical pattern.
- Anterior arc (to Nasion) — Radius from point O to Nasion; establishes the baseline arc against which the other facial landmarks are compared.
- ANS arc and "A" arc (to Point A) — Compare the maxillary anterior nasal spine and Point A position to the anterior arc; deviations indicate maxillary anteroposterior excess or deficiency relative to the vertical pattern.
- Midfacial arc (to Temporale) — Assesses the midface position relative to the same reference geometry.
- Posterior arc (to Sella posterior wall) — Confirms the cranial base contribution to the overall arc system.
- Divergence angle — The angle formed between the reference planes at their point of intersection (or near-intersection); a widening (divergent) angle is associated with long-face/open-bite tendencies, while a narrowing (convergent) angle is associated with short-face/deep-bite tendencies.
Learn more: SpeedyCeph Knowledgebase — Sassouni arc constructions (Anterior, Posterior, Basal, Midfacial arcs)
Clinical Interpretation
Rather than asking "is this angle bigger or smaller than the textbook average," the Sassouni analysis asks "do this patient's own planes and arcs agree with each other." When the four horizontal planes nearly converge at a single point O, the clinician can treat the case as having a balanced vertical pattern, meaning aligner staging and bite-opening/closing mechanics can follow standard assumptions. When the planes fail to converge — fanning open posteriorly — this signals a divergent (long-face) pattern prone to anterior open bite and higher relapse risk with vertical elastics or extrusive mechanics; when the planes converge sharply anterior to a true intersection, it signals a convergent (short-face) pattern prone to deep bite. Because the arcs from point O also flag anteroposterior discrepancies (e.g., Point A sitting outside its expected arc), the same diagram lets the clinician cross-check sagittal classification against vertical pattern in one view, which is why the method remains popular for orthognathic surgical planning and for cases with a combined vertical and sagittal skeletal problem.
Learn more: Geometric morphometric analysis of growth patterns among facial types (PMC)