<prompt> Most common epicenter of a radicular cyst is:Distal surface of toothApex of tooth involvedMesial surface of toothDeep periodontal pocket  <response>: In most cases, the epicenter of a radicular cyst is located approximately at the apex of a nonvital tooth. It occasionally appears on the mesial or distal surface of a tooth root at the opening of an accessory canal or infrequently in a deep periodontal pocket. Oral radiology White and Pharaoh; 7th ed. Page no 335 