Wits Appraisal
The Wits appraisal is a cephalometric measurement introduced by Alexander Jacobson in 1975 while at the University of the Witwatersrand in Johannesburg (the name "Wits" is an abbreviation of the institution). It was developed to overcome a known weakness of the ANB angle, which can be distorted by variations in the vertical position of Nasion that have nothing to do with the actual jaw discrepancy.
Instead of referencing the cranial base, the Wits appraisal measures the anteroposterior relationship between the maxilla and mandible directly against the patient's own occlusal plane, making it a useful cross-check in borderline or ambiguous Class II/Class III cases.
What It Evaluates
The Wits appraisal quantifies how far forward or backward the maxilla sits relative to the mandible, independent of cranial base anatomy or Nasion position. It is typically used alongside — not instead of — the ANB angle, since the two measurements can disagree when the cranial base is atypical.
Key Measurements
- AO — the point where a perpendicular dropped from cephalometric point A (maxilla) meets the functional occlusal plane.
- BO — the point where a perpendicular dropped from cephalometric point B (mandible) meets the functional occlusal plane.
- Wits value (AO − BO) — the linear distance between AO and BO along the occlusal plane. Normal values are close to zero, with a slight sex difference: males average +1 mm (SD ±1.9 mm), females average 0 mm (SD ±1.77 mm).
- Functional occlusal plane — the reference line drawn through the cusp tips of the most posterior teeth in occlusion (typically the first molars and premolars), used instead of the cranial base as the plane of measurement.
Learn more: Wits Analysis — Cephalometric Services Platform, analyzeceph.com
Clinical Interpretation
A positive Wits value means AO lies ahead of BO — the maxilla is positioned forward relative to the mandible, consistent with a Class II skeletal tendency. Values of roughly +4 to +6 mm suggest a moderate discrepancy, and values above +8 mm suggest a severe one.
A negative Wits value means BO lies ahead of AO — the mandible is positioned forward relative to the maxilla, consistent with a Class III skeletal tendency. Values below about −4 mm (males) or −3 mm (females) suggest a moderate discrepancy, with values below −6 mm indicating severity.
Because the Wits appraisal depends on accurate identification of the functional occlusal plane, it is sensitive to how that plane is drawn — a key reason it is used to complement, rather than replace, angular measurements like ANB.
Learn more: WITS APPRAISAL — Dentistry 'N More (YouTube)