An X-ray shows a tooth with a very short, thick root, obliterated pulp chamber, no radiolucency, and no associated pathology. What is the most likely explanation?

Correct answer: D. Insufficient root development (dens invaginatus / incomplete root formation)

• A. Hypercementosis shows excess cementum at the apex (club-shaped root), not a short thick root with obliterated pulp.
• B. Dentinogenesis imperfecta shows obliterated pulp chambers but is associated with characteristic opalescent discoloration and is typically a diagnosis made across multiple teeth.
• C. External root resorption would show loss of root structure from outside in, not a uniformly short thick root.
• D. Correct. Short, thick roots with obliterated pulp chambers and no associated pathology in an otherwise normal-appearing tooth suggest an anomaly of root development such as dens invaginatus (dens in dente) or, per the source context, 'insufficient root development.' This was the answer chosen by the source when dentigerous imperfecta and DD were not options.