Background: Ectopic eruption of a tooth or osteoma rarely occurs within the maxillary sinus. Coexistence of these two rare entities in the maxillary sinus has never been reported in the English literature.
Case Report: Herein, we present a 21 year-old male patient with osteoma and ectopic tooth in the left maxillary sinus treated with the removal of the ectopic tooth by endoscopic sinus surgery and excision of the osteoma by the Caldwell- Luc procedure.
Conclusion: Unique coexistence of two different entities in the maxillary sinus is most likely due to pediatric facial trauma. Pediatric patients with maxillofacial trauma should be carefully watched for dental injury both clinically and radiologically.