Pathology · single question

Each of the following is true of taurodontism EXCEPT one. Which is the EXCEPTION?

Both permanent and primary teeth may be affected
The pulp chamber is enlarged because the furcation is displaced occlusally
The unusual root form results from delayed or failed invagination of Hertwig epithelial root sheath
It occurs in patients with amelogenesis imperfecta and Down syndrome

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Correct answer: B. The pulp chamber is enlarged because the furcation is displaced occlusally

A. This IS true. Although far more commonly noted in permanent molars, primary molars can be affected.
B. CORRECT — this is the EXCEPTION. The furcation in taurodontism is displaced APICALLY, not occlusally. That apical displacement is precisely what elongates the pulp chamber vertically and shortens the roots, producing the characteristic 'bull tooth' rectangular chamber.
C. This IS true. Hertwig epithelial root sheath fails to invaginate at the proper horizontal level, so root furcation forms late and low.
D. This IS true. Taurodontism is associated with amelogenesis imperfecta, Down syndrome, Klinefelter syndrome, and tricho-dento-osseous syndrome.

Note: Apical furcation displacement is the single defining feature — every other finding follows from it.

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