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Deciduous Tooth Ankylosis — MFDS Part 1 MCQ

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ModerateAnatomy (Head & Neck)Deciduous Tooth AnkylosisMFDS Part 1

An 8-year-old child has a mandibular primary second molar that lies below the adjacent occlusal plane. The tooth is firm and produces a high, metallic note on percussion. Which pathological change most likely accounts for these findings?

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Correct answer: E — Direct fusion of the root surface to alveolar bone with local obliteration of the periodontal ligament

The correct answer is E. Dental ankylosis is direct union of the root surface—cementum or, in some areas, dentine—with alveolar bone, accompanied by local loss of the periodontal ligament. The tooth therefore lacks normal periodontal mobility and cannot maintain its position relative to the occlusal plane during continuing dentoalveolar growth, producing progressive infraocclusion and a characteristically solid or metallic percussion note. Periodontal ligament widening would cause mobility rather than fixation. Physiological root resorption leads toward exfoliation, not rigid attachment to bone. Hypercementosis retains a periodontal ligament and does not itself explain infraocclusion. External inflammatory resorption is also distinct from ankylosis while a periodontal ligament space remains present.

Reference: Eşian D et al. Prevalence and Manifestations of Dental Ankylosis in Primary Molars Using Panoramic X-rays: A Cross-Sectional Study. Children. 2022;9(8):1188. https://pubmed.ncbi.nlm.nih.gov/36010078/