Primary Dentition Crossbite — ORE Part 1 MCQ

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ModerateOrthodonticsPrimary Dentition CrossbiteORE Part 1

A child in the primary dentition has a unilateral posterior crossbite. Which underlying transverse discrepancy is most commonly present?

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Correct answer: B — Reduced maxillary arch width

The best answer is B. A posterior crossbite represents a transverse discrepancy, and affected children commonly have a reduced maxillary arch width relative to the mandible. In deciduous-dentition cohorts, smaller maxillary arch width was significantly associated with unilateral posterior crossbite. Prolonged non-nutritive sucking may contribute to narrowing and is an important risk factor, but digit sucking is not the most consistently implicated habit; pacifier use has a clearer association. Forward or low tongue posture may also contribute, but it is not the defining transverse discrepancy. Nasal obstruction and otological disease are not established primary explanations for a posterior crossbite; impaired nasal breathing was not significantly associated in the cited deciduous-dentition study.

Reference: Melink S, Velikonja Vagner M, Hocevar-Boltezar I, Ovsenik M. Posterior crossbite in the deciduous dentition period, its relation with sucking habits, irregular orofacial functions, and otolaryngological findings. American Journal of Orthodontics and Dentofacial Orthopedics. 2010. https://pubmed.ncbi.nlm.nih.gov/20620831/