Potential adverse consequence of rapid maxillary expansion (RME)

 # One potential adverse consequence of rapid maxillary expansion (RME) in a patient nearing skeletal maturity is an increase in:

A. Anterior Bolton Ratio Discrepancy

B. Apical Base Width

C. Mandibular Plane Angle

D. Palatal Vault Depth

The correct answer is C. Mandibular Plane Angle

In patients nearing skeletal maturity, the midpalatal suture is partially or fully interdigitated, reducing skeletal expansion efficacy and promoting dentoalveolar effects like buccal tipping and posterior molar extrusion (1–2 mm on average), which increases the mandibular plane angle (MPA) by 1–3° via clockwise mandibular rotation and bite opening. This vertical change exacerbates hyperdivergent tendencies, potentially worsening facial height and stability, as noted in cephalometric studies of late mixed/early permanent dentition cases. In contrast, apical base width (B) is the intended skeletal gain (though diminished); anterior Bolton discrepancy (A) is unrelated; and palatal vault depth (D) typically decreases with RME due to transverse widening.