A periapical radiograph shows an invagination of enamel and dentin into the crown of a maxillary lateral incisor, creating a radiopaque-lined pocket extending toward the pulp. What is this anomaly?

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

• A. Dens evaginatus is the opposite: an OUTWARD tubercle of enamel and dentin containing a pulp horn, most common on mandibular premolars in Asian and Native American populations.
• B. CORRECT. DENS INVAGINATUS results from infolding of the enamel organ into the dental papilla BEFORE calcification. The maxillary LATERAL INCISOR is by far the most commonly affected tooth. The invagination creates a communication with the oral cavity, so bacteria track into a defect near the pulp — producing pulp necrosis in a tooth that appears caries-free and un-traumatized. Prophylactic sealing of the pit is the preventive treatment.
• C. Concrescence is the union of two adjacent teeth by CEMENTUM only, after root formation.
• D. Fusion is the union of two separate tooth germs, giving a reduced tooth count.

Note: Necrotic anterior tooth in a teenager with no caries and no trauma history? Look hard for a dens invaginatus pit on the lingual.