An 84-year-old patient's radiographs show amalgams in most posterior teeth. On one posterior molar roughly half of the coronal tooth/restoration appears gone. What most likely happened to that molar?

Correct answer: C. The restoration was lost (missing/fractured-out restoration)

• A. Recurrent caries can occur, but the described picture (restoration appears to have 'fallen out') points specifically to a missing restoration.
• B. Internal resorption is an intra-radicular/coronal radiolucent process, not the loss of an amalgam filling.
• C. Correct. The appearance of a large amalgam that looks as if part of the crown is 'missing' is most consistent with a LOST/dislodged restoration, leaving an empty cavity preparation where the filling used to be.
• D. Congenital malformation would have been present lifelong, not a sudden change in a restored tooth.