What is the most common indication for an X-ray of a multilocular radiolucent lesion in the posterior mandible?

The most common indication for an X-ray of a multilocular radiolucent lesion in the posterior mandible is indeed associated with the presence of an ameloblastoma. Ameloblastomas commonly manifest as multilocular radiolucent lesions in the jaw, particularly in the posterior mandible, and are often asymptomatic at first. The X-ray appearance of these lesions is distinctive and can help in diagnosis, as they typically present with a "soap bubble" or "honeycomb" appearance due to the multilocular nature of the tumor.

While cysts and keratocysts can also present as multilocular lesions, ameloblastomas are more frequently encountered in this context, making them a key consideration for diagnostics in dental practice. Osteosarcoma, although potentially present in the mandible, generally exhibits a different radiographic pattern and is less commonly encountered than ameloblastoma in this specific scenario.