Correction of a severe anterior open bite in an adult through combined orthodontic and orthognathic surgery

 # Correction of a severe anterior open bite (greater or equal to 4 mm) in an adult through combined orthodontic and orthognathic surgery (e.g. Le Fort I impaction) primarily improves masticatory function by:

A. Increasing the number of simultaneous bilateral posterior occlusal contacts

B. Increasing the vertical dimension of occlusion

C. Eliminating the need for tongue-thrust habit adaptation

D. Preventing future TMJ derangement and pain

The correct answer is A. Increasing the number of simultaneous bilateral posterior occlusal contacts

Severe anterior open bite in adults often stems from vertical maxillary excess, leading to reduced or eccentric posterior occlusal contacts due to mandibular posturing or supraeruption, which impairs efficient bolus grinding and mixing during mastication (e.g., 20-40% lower chewing cycles for particle size reduction pre-treatment). Combined orthodontic-orthognathic intervention, such as Le Fort I impaction with mandibular autorotation, closes the anterior gap while enhancing posterior coupling—typically increasing functional contact points by 2-3 pairs per quadrant—as confirmed by pre/post-surgical occlusal analyses and electromyographic studies showing 30-50% gains in masticatory efficiency. This restores symmetric force distribution and excursion freedom, outperforming habit correction (C, adjunctive at best) or VDO changes (B, actually decreased here); TMJ benefits (D) are secondary and inconsistent.