Abstract: PURPOSE: This study was aimed to review the location and differential diagnosis of odontogenic cysts intruding into maxillary sinus, in order to improve accuracy rate of preoperative diagnosis and guide operation planning. METHODS: Cases of odontogenic cysts intruding into sinus diagnosed by spiral CT from 2011.12 to 2014.12 at the Department of Oral Surgery, Shanghai Ninth People’s Hospital were reviewed. The proportion of each sinus wall being invaded was counted using spiral CT images. Then selecting the ones with pathologic diagnosis and analyzing their CT images, along with clinical manifestation to summarize the entities and differential diagnosis of odontogenic cysts. RESULTS: A total of 85 cases were included, the inferior and posterior walls of the sinus were most frequently invaded, and the top three disease entities were dentigerous cyst, radicular cyst and odontogenic keratocystic tumor. Two cases diagnosed as ameloblastoma but turned out to be adenoid cystic carcinoma and mucoepidermoid carcinoma after pathological examination. CONCLUSIONS: Odontogenic cysts often intrudes into inferior and posterior walls of maxillary sinus, diagnosis should depend on CT images and pathological examinations, as well as clinical manifestation.

Key words: Maxillary sinus, Odontogenic cysts, Spiral CT, Differential diagnosis