Eastman Analysis

The Eastman analysis was developed at the Eastman Dental Institute (now UCL Eastman Dental Institute) in London, building on earlier work by Ballard, who studied 250 London schoolchildren, later refined by Mills in 1970. It remains the analysis most widely taught in UK orthodontic training programmes and is commonly expected knowledge in Royal College of Surgeons postgraduate examinations.

Unlike Steiner's analysis, which was standardized on a small American sample, the Eastman analysis was normed against a British Caucasian population, and it evaluates incisor position relative to the jaw planes rather than purely to the cranial base — an approach many clinicians find more intuitive for treatment planning.

What It Evaluates

The Eastman analysis assesses three things together: the anteroposterior relationship of the jaws to the cranial base and to each other, the vertical proportions of the face (how "open" or "closed" the bite pattern is), and the position of the upper and lower incisors relative to their supporting jaw planes.

Learn more: A Beginner's Guide to Lateral Cephalometric Radiographs — Dental Protection

Key Measurements

  • SNA — position of the maxilla relative to the cranial base. Normal: 81° ± 3°.
  • SNB — position of the mandible relative to the cranial base. Normal: 79° ± 3°.
  • ANB — the difference between SNA and SNB, describing the sagittal (anteroposterior) relationship between the jaws. Normal: 3° ± 2° (Class I); above 4° suggests Class II, below 2° suggests Class III.
  • MMPA (Maxillary-Mandibular Plane Angle) — the angle between the maxillary and mandibular planes, describing vertical facial proportion. Normal: 27° ± 4°.
  • UI/MxP — upper incisor inclination to the maxillary plane. Normal: 109° ± 6°.
  • LI/MnP — lower incisor inclination to the mandibular plane. Normal: 93° ± 6°.
  • Interincisal angle — the angle between the long axes of the upper and lower incisors. Normal: 135° ± 10°.
  • Eastman correction (Mills, 1970) — an adjustment applied to SNA when Nasion sits in an atypical vertical position but the SN/maxillary plane angle is otherwise normal, preventing a misleading skeletal reading.

Learn more: Eastman correction – Mills Correction (Cephalometric analysis) — M Nassim ALhibishy (YouTube)

Clinical Interpretation

ANB classifies the sagittal skeletal pattern: values within 2°–4° are Class I, above 4° indicate a Class II skeletal base (maxilla relatively forward), and below 2° indicate a Class III skeletal base (mandible relatively forward).

MMPA classifies the vertical growth pattern, which strongly influences mechanics and anchorage choices: high-angle (>31°) is associated with a longer lower face and a tendency toward open bite, average (23°–31°) reflects balanced proportions and normal overbite, and low-angle (<23°) is associated with a shorter lower face and a tendency toward deep bite.

The incisor angulations (UI/MxP and LI/MnP) tell the clinician how upright or proclined the incisors already are relative to their normal ranges, which directly informs how much torque or tip correction is needed during treatment planning — particularly relevant when deciding on extraction versus non-extraction mechanics.

Learn more: Diagnostic performance of various cephalometric parameters for the assessment of vertical growth pattern — PMC

References