Ectopic maxillary third molar associated with an odontogenic keratocyst in the maxillary Sinus presenting as refractory unilateral sinonasal symptoms: a case report with implications for early dental diagnosis.

Background: Ectopic teeth in the maxillary sinus are relatively rare, most commonly seen in the third molars, often accompanied by odontogenic cysts and presenting with symptoms similar to chronic sinusitis, which are easily misdiagnosed or overlooked. Cases: A 24-year-old female patient presented with purulent nasal discharge and recurrent swelling of the right side of the face for 2 years. Despite multiple courses of antibiotic treatment, her symptoms showed little improvement. Clinical examination revealed the absence of the right maxillary third molar. Panoramic x-ray showed a tooth-like high-density shadow in the right maxillary sinus, surrounded by soft tissue density. Cone beam computed tomography (CBCT) further confirmed the presence of an ectopic third molar in the right maxillary sinus, accompanied by a cystic lesion. The patient underwent surgical removal of the ectopic tooth and complete excision of the cyst under general anesthesia via an intraoral approach. Postoperative histopathological examination confirmed the diagnosis of odontogenic keratocyst. The patient's symptoms completely resolved after surgery, and a 6-month postoperative CBCT review showed good pneumatization of the right maxillary sinus with no signs of recurrence. Conclusion: For persistent unilateral sinus symptoms that are unresponsive to conventional medical treatment, the presence of an ectopic maxillary third molar with an odontogenic cyst should be considered. Good clinical outcomes can be achieved by surgically removing the ectopic tooth and the associated cyst. This case also suggests that when tooth eruption is abnormal, early imaging evaluation is of significant value.