Unilateral posterior crossbite with mandibular displacement — ORE Part 1 MCQ
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Correct answer: C — Orthodontic referral for early crossbite correction
The correct answer is C: Orthodontic referral for early crossbite correction. This 9-year-old presents with a functional (positional) unilateral posterior crossbite characterised by a mandibular shift on closure—a key finding that occurs when the dentition forces the mandible laterally from centric relation into intercuspal position. Evidence clearly shows that such crossbites do not self-correct and require early intervention. The quad-helix appliance is the gold-standard treatment in mixed dentition, offering superior success rates and shorter treatment duration compared to removable plates. Early treatment eliminates the functional displacement, prevents asymmetrical development, and maintains stability on long-term follow-up. Option A is wrong because spontaneous correction does not occur and the condition will persist into adulthood. Option D (crowns) is ineffective and invasive. Option B (extraction) is destructive and unnecessary. Option E (incisor equilibration) does not address the posterior crossbite.
Reference: Harrison JE, Ashby D, Craft A. Orthodontic treatment for posterior crossbites. Cochrane Database Syst Rev. 2014;(1):CD000979; also: Petrén S, et al. Correction of unilateral posterior crossbite in the mixed dentition: a randomized controlled trial. Am J Orthod Dentofacial Orthop. 2008;133(6):813–817. https://pubmed.ncbi.nlm.nih.gov/18538237/