Eastman Analysis: A Complete Cephalometric Guide

History and Origins of the Eastman Analysis

The Eastman analysis was developed at the Eastman Dental Institute (now the UCL Eastman Dental Institute) in London — one of the most influential postgraduate dental centres in Europe. The analysis emerged from the clinical and teaching needs of British orthodontic training programmes in the latter half of the twentieth century, drawing on the foundational work of Steiner, Ballard, and Mills while refining the framework for a European clinical context.

Unlike Steiner's analysis, which was designed for an American clinical setting using norms derived from a small white American sample, the Eastman analysis was standardised against British Caucasian populations. This distinction matters clinically: normative values differ between populations, and applying American norms to British or European patients introduces systematic diagnostic bias. The Eastman analysis addressed this directly by deriving its own reference values from the population it was intended to serve.

Today, the Eastman analysis is the standard cephalometric analysis taught across most UK orthodontic training programmes and is widely used in European and Commonwealth clinical practice. It appears in the membership examinations of the Royal College of Surgeons of England and is the analysis framework expected in most British orthodontic case presentations.

Why the Eastman Analysis Was Developed

The Eastman analysis was developed to address three specific limitations of the Steiner system when applied outside the American clinical context:

• Population-specific norms. Steiner's normative values (SNA 82°, SNB 80°, ANB 2°) were derived from a small American sample. British and European populations show slightly different craniofacial proportions. The Eastman norms (SNA 81°, SNB 79°, ANB 3°) reflect these population differences and provide more accurate diagnostic thresholds for the patients most UK and European orthodontists treat.
• Incisor measurement philosophy. Steiner relates incisors to the NA and NB lines — references that are anchored to the cranial base via Nasion. The Eastman analysis instead relates upper incisors to the maxillary plane and lower incisors to the mandibular plane. This approach is more intuitive for treatment planning because incisor torque is mechanically expressed relative to the jaw base, not the cranial base. The clinician can read the incisor-to-jaw-plane angle and directly assess how much torque change is required.
• Vertical dimension assessment. Steiner analysis has no dedicated vertical measurement. The Eastman analysis includes the Maxillary-Mandibular Planes Angle (MMPA) as a core measurement, giving the clinician immediate information about facial divergence pattern — a critical factor in mechanics selection, anchorage planning, and extraction decisions.

Key Landmarks and Reference Planes

The Eastman analysis uses the following anatomical landmarks on a standard lateral cephalogram:

Skeletal Landmarks

• Sella (S) — the geometric centre of the pituitary fossa.
• Nasion (N) — the most anterior point of the frontonasal suture.
• A point (Subspinale) — the deepest concavity on the anterior contour of the maxilla.
• B point (Supramentale) — the deepest concavity on the anterior contour of the mandibular symphysis.
• ANS (Anterior Nasal Spine) — the tip of the anterior nasal spine of the maxilla.
• PNS (Posterior Nasal Spine) — the most posterior point of the hard palate.
• Gonion (Go) — the most posterior-inferior point on the angle of the mandible.
• Menton (Me) — the lowest point on the mandibular symphysis.

Dental Landmarks

• U1 tip and apex — the incisal edge and root apex of the most prominent upper central incisor.
• L1 tip and apex — the incisal edge and root apex of the most prominent lower central incisor.

Reference Planes

• SN plane (S–N) — the anterior cranial base reference for skeletal measurements.
• Maxillary plane (ANS–PNS) — the palatal plane, used as the reference for upper incisor angulation and for the SN-to-maxillary-plane angle.
• Mandibular plane (Go–Me) — used as the reference for lower incisor angulation and for the MMPA.

Eastman Analysis Measurements and Normative Values

The table below presents the complete set of Eastman analysis measurements with their normative values and clinical significance.

Skeletal Measurements

Dental Measurements

Clinical Interpretation: How Eastman Guides Treatment Planning

The MMPA and Vertical Planning

The MMPA is arguably the most clinically consequential measurement unique to the Eastman analysis. It determines the vertical category of the patient — average, high-angle, or low-angle — which directly influences every subsequent treatment decision. High-angle patients (MMPA >31°) require mechanics that avoid further opening of the bite: intrusion rather than extrusion, avoidance of Class II elastics where possible, and consideration of TADs for molar intrusion. Low-angle patients (MMPA <23°) can tolerate extrusive mechanics and often present deep bites that require molar extrusion or incisor intrusion.

The MMPA also modifies the interpretation of the incisor measurements. In a high-angle case, lower incisors that appear proclined (LI to MnP >93°) may actually be compensating for the divergent skeletal pattern — and retroclining them risks worsening the vertical discrepancy. This is why the Eastman system considers skeletal and dental measurements as an integrated unit, not in isolation.

Incisor-to-Jaw-Plane: Treatment Targets

Relating incisors to their own jaw planes makes treatment target-setting intuitive. If UI to MxP is 120° (proclined beyond the 109° ± 6° norm), the clinician knows immediately that the upper incisors need approximately 11° of retroclination — expressed as palatal root torque in the appliance prescription. This is mechanically direct: the maxillary plane is the bone the bracket sits on, and the torque is expressed relative to that bone.

In contrast, Steiner's U1–NA measurement references a line from Nasion to A-point — a geometric construction that doesn't correspond to any mechanical reality of the appliance. This is why many UK-trained orthodontists find Eastman more practical for day-to-day treatment planning, even if they use Steiner for case documentation and academic communication.

The Interincisal Angle as a Stability Indicator

A reduced interincisal angle (<125°) in the Eastman system signals bimaxillary proclination — both upper and lower incisors are tipped forward of their jaw bases. This pattern has implications for treatment stability: proclined incisors are under lip pressure and tend to relapse lingually. The Eastman interincisal angle, combined with the individual UI/MxP and LI/MnP readings, gives the clinician three independent measures of incisor position to plan a stable post-treatment result.

Eastman vs. Steiner: When to Use Which

The two analyses share the same skeletal framework (SNA, SNB, ANB on the SN plane) but differ in their dental measurements, normative values, and clinical philosophy. The comparison below helps clinicians decide which analysis — or combination — to apply.

In practice, many experienced clinicians run both analyses from the same set of landmarks. Steiner provides the universally understood skeletal classification and the compromise concept for incisor positioning. Eastman provides population-appropriate norms, vertical classification via MMPA, and mechanically intuitive incisor targets. BCeph computes both simultaneously — no duplicate landmark placement required.

Frequently Asked Questions