Measurement · WITS
Wits appraisal (AO–BO)
Loading the reference ceph.
Definition
The distance between the perpendicular projections of A point (AO) and B point (BO) onto the occlusal plane. Positive = AO ahead of BO (Class II direction); ~0 is normal.
How
Drop perpendiculars from A and B onto the occlusal plane; label the feet AO and BO. Measure AO–BO along the plane. Norms: ♂ ≈ −1 mm, ♀ ≈ 0 mm.
Purpose
A jaw-relationship read that bypasses Nasion and the cranial base entirely — its whole reason to exist. When ANB and Wits disagree, suspect a cranial-base/vertical rotation artifact in ANB; Wits is the tie-breaker (but it inherits any error in the occlusal plane, especially in mixed dentition).
High
Above the norm reads as AO well ahead of BO — skeletal Class II discrepancy at the occlusal level.
Low
Below the norm reads as BO ahead of AO — skeletal Class III discrepancy.
Built from
Listed by Steiner, Skeletal A-P, Wits.
This is a reviewed tracing on one real cephalogram — the same ceph on every page in Learn — so Wits appraisal (AO–BO) here is a real reading and not a diagram.