Posterior Crossbite Correction — ORE Part 1 MCQ

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ModerateOrthodonticsPosterior Crossbite CorrectionORE Part 1

A 14-year-old patient has a unilateral posterior crossbite with a mandibular shift on closure. The maxillary arch is narrow. What is the most appropriate initial orthodontic treatment?

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Correct answer: D — Maxillary expansion to correct the transverse maxillary deficiency

Explanation lettering: E = shown as A · C = shown as B · D = shown as C · A = shown as D · B = shown as E

In a 14-year-old with unilateral posterior crossbite, mandibular functional shift, and narrow maxilla, the underlying skeletal problem is transverse maxillary deficiency. Maxillary expansion is the evidence-based initial treatment. It addresses the structural cause, allowing the mandible to normalise its position and preventing long-term craniofacial asymmetry. RME or quad-helix appliances are superior to slow expansion for this age group and dentition stage. Fixed appliances (B) are applied after expansion to refine occlusion. Functional appliances alone (C) do not correct maxillary width. Headgear (D) addresses sagittal relationships, not transverse deficiency. Surgery (E) is inappropriate in a growing adolescent with remaining skeletal potential.

Reference: Early Orthodontic Treatments of Unilateral Posterior Crossbite: A Systematic Review (2020). NCBI/PMC articles; and Correction of unilateral posterior crossbite in the mixed dentition: a randomized controlled trial, American Journal of Orthodontics and Dentofacial Orthopedics (2008). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7795353/ and https://pubmed.ncbi.nlm.nih.gov/18538237/