Which condition is most commonly associated with a J-shaped radiolucency on a dental radiograph?

A J-shaped (or halo-shaped) radiolucency on a periapical radiograph is the classic radiographic sign of a vertical root fracture. The J-shape forms because the fracture allows bone destruction along the length of the root as well as at the apex, creating a radiolucency that extends from the apex upward along the lateral surface of the root, resembling the letter J. Other radiographic signs of vertical root fracture include a widened periodontal ligament space, thickening of the lamina dura, and halo lesions around the root. Vertical root fractures often occur in endodontically treated teeth and are associated with excessive lateral condensation forces.