What is the most probable diagnosis for a firm, painless swelling located at the midline of the hard palate that shows up as radiopaque on an X-ray?

Explanation

The described lesion is a torus palatinus, which is a benign, bony protuberance found along the midline of the hard palate. It is typically asymptomatic and appears radiopaque on radiographic images, distinguishing it from odontomas, myxomas, or cystic bone lesions.