Which developmental anomaly is MOST likely to lead to early pulpal necrosis and apical periodontitis?

Correct answer: A. Dens invaginatus (dens in dente)

• A. CORRECT. DENS INVAGINATUS is an infolding of enamel organ into the dental papilla before mineralisation, creating a deep invagination — most often in a maxillary LATERAL INCISOR — that communicates with the oral cavity. The lining is thin, frequently defective enamel and dentine, so bacteria track directly to the pulp. Pulpal necrosis and a periapical lesion can therefore develop in a tooth that is CARIES-FREE and recently erupted, which is exactly why it is the classic answer to this question. Prophylactic sealing of the invagination at eruption prevents it.
• B. ENAMEL PEARLS are ectopic enamel nodules, usually at furcations. They are a PERIODONTAL problem — they prevent connective tissue attachment and promote localised pocketing — not a pulpal one.
• C. DENS EVAGINATUS is a tubercle projecting from the occlusal surface, most often on a mandibular premolar, containing a pulp horn. It CAN cause necrosis when the tubercle fractures or wears, so it is a legitimate second choice — but dens invaginatus is the more classical and more direct answer, since the communication is present from eruption rather than requiring wear or fracture.
• D. TAURODONTISM alters the shape of the pulp chamber and complicates endodontic access, but it does not create a pathway for bacterial ingress and does not predispose to necrosis.

Note: Both anomalies argue for the same preventive action: identify them at eruption and seal or selectively reduce them prophylactically, before the pulp is compromised. Dens evaginatus is notably common in patients of East Asian and Native American descent.