The Endo-Antral Connection: Understanding the role of endodontic infections in maxillary sinus disease. Description: The pathological extension of periapical infection into the maxillary sinuses is often overlooked in clinical medical and dental practice, with its sequelae often misdiagnosed as rhinogenic sinusitis. This lecture explains and illustrates the similarities, distinguishing differences, and frequent inter-relationship between endodontic disease and paranasal sinus infections. The associated clinical and radiographic findings of maxillary sinusitis of endodontic origin (MSEO) are explained using many real-world clinical case examples with an update on the current literature. Emphasis is placed on the importance of CBCT imaging, magnification, proper terminology, and clinical expertise for rendering both non-surgical and surgical endodontic treatment when indicated. The goal is to help practitioners distinguish rhinosinusitis from odontogenic sinusitis, and specifically MSEO, in an effort to improve the health of patients through accurate diagnosis, appropriate treatment, and improved communication between endodontists and ENT specialists