Benefit of orthodontic-surgical correction of a severe skeletal Class III

 # The benefit of orthodontic-surgical correction of a severe skeletal Class III is the ANB change. This change is best described as a combination of a surgically induced forward change in SNA and a:

A. Surgically-induced forward change in SNB

B. Vertical increase in posterior facial height

C. Surgically-induced backward change in SNB

D. Orthodontically-induced posterior dental rotation

The correct answer is C. Surgically-induced backward change in SNB

In severe skeletal Class III malocclusion, bimaxillary orthognathic surgery typically combines Le Fort I maxillary advancement (increasing SNA by 3–6 mm forward positioning) with bilateral sagittal split osteotomy (BSSO) mandibular setback (reducing SNB by 4–8 mm posteriorly), yielding a net ANB increase of 4–7° for Class I stability. Cephalometric studies confirm this dual skeletal adjustment as the primary mechanism for profile normalization and airway enhancement, with mandibular setback countering inherent prognathism without solely relying on maxillary protraction (which risks relapse). Vertical height changes (B) address secondary open bite but minimally impact ANB; forward SNB (A) would exacerbate discrepancy; and dental rotations (D) are pre-surgical adjuncts, not core to skeletal ANB gains.