Pediatric Dentistry · single question
What causes bilateral posterior open bite?
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Correct answer: C. Ankylosis of primary molars
Ankylosis of primary molars prevents their normal occlusal eruption/migration as the jaw grows. The adjacent teeth and alveolar bone continue to erupt and grow vertically, but the ankylosed tooth remains 'stuck' below the plane of occlusion (infraocclusion). This progressive submergence creates a bilateral posterior open bite, as the surrounding dentition over-erupts while the ankylosed teeth cannot migrate.
- A. CORRECT. Ankylosed primary molars cause infraocclusion and bilateral posterior open bite because they cannot migrate with normal alveolar growth.
- B. Incorrect. Tongue thrusting causes ANTERIOR open bite — the tongue sits between the upper and lower anterior teeth during swallowing, preventing incisor contact.
- C. Incorrect. A retained primary tooth over an unerupted permanent tooth may cause localized space/position issues but not a bilateral pattern of posterior open bite.
- D. Incorrect. An amalgam overhang would cause periodontal irritation, not a bilateral posterior open bite pattern.
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