A radiograph of the mandibular anterior region shows two crowns joined with a shared structure. If the total tooth count in the arch is NORMAL, what is the diagnosis?

Correct answer: B. Gemination

• A. Incorrect. Fusion is union of TWO separate tooth germs, so the arch shows one tooth FEWER than normal when the anomaly is counted as one.
• B. Correct. Gemination is incomplete division of a SINGLE tooth germ. Counting the anomaly as one tooth gives a NORMAL total count. Usually there is one root and one canal.
• C. Incorrect. Dens invaginatus is an infolding of enamel into the crown, producing a 'tooth within a tooth' appearance, typically in maxillary lateral incisors.
• D. Incorrect. Concrescence is union by CEMENTUM only, with separate crowns and separate pulp chambers — most common in maxillary molars.

Note: 📌 The counting rule is the whole question: count the anomalous structure as ONE tooth. Normal total = gemination. One tooth missing = fusion. (Fusion can also occur with a supernumerary, which confounds the count — hence 'usually'.)