A radiograph of premolar tooth #5 shows a clear horizontal fracture line in the middle third of the root. What is the most likely diagnosis?

A transverse radiolucent line crossing the mid-root indicates a horizontal root fracture.Other options: Caries appears at the crown/cervical region; internal resorption shows a ballooning of the canal; condensing osteitis is periapical sclerosis.Key exam takeaway: A transverse line across the root = horizontal root fracture.