An oro-antral fistula is an abnormal communication between the oral cavity and maxillary sinus. It is commonly caused by tooth extractions or trauma to the face. Symptoms include escape of fluids or air from the sinus, pain, and discharge. Diagnosis involves tests like blowing the nose to feel air escape from the mouth. Treatment first requires eliminating any sinus infection, then surgically excising the fistula tract and closing the bony defect, often using local soft tissue flaps or bone grafts. The buccal advancement flap and palatal transpositional flap are commonly used procedures.