Purpose: To present a retrospective case series of displaced dental implants in the maxillary sinus. Materials and methods: Patients with unintentional displacement of dental implants in the maxillary sinus over a 5-year period who underwent or were candidates for surgical implant removal were included. The patients' characteristics, medical history, clinical and imaging results, and post-removal outcome were retrospectively assessed. Results: Out of 14 patients, 13 underwent surgical removal. In one case the implant spontaneously exiled into the nose before surgery. The timespan between dental implantation and presentation ranged from 3 months to 9 years. Imaging evaluation showed a displaced implant (100%), oroantral fistula (65%), complete opacification of the maxillary sinus (28%), circumferential opacification (21%), isolated maxillary sinus outflow obstruction (7%) and a sinus which appeared normal (43%). Symptoms and signs included nasal obstruction (36%), purulent secretions (36%), facial pain (21%), tenderness on percussion (21%) and foul smell (14%). Two patients (14%) were asymptomatic. Intraoperative inspection of nine sinuses revealed mucosal changes and purulent secretions in 55% of patients. In all cases the implant had migrated from the maxillary sinus floor towards the natural ostium. Endoscopic removal was carried out successfully in all operated cases. All sinuses eventually healed. Conclusions: Migration of displaced implants and mucosal changes may occur over a short period, eventually causing secondary sinusitis. We therefore favour surgical removal. Surgery should be as close as possible to displacement in order to minimise mucosal inflammation and to prevent unnecessary manipulation during surgical removal. Schlagwörter: dental implant, endoscopic sinus surgery, foreign body, maxillary sinus, sinusitis Conflict of interest statement: None of the authors report any financial interests or potential conflict of interests.