[Abstract]Six patients with iatrogenic and noniatrogenic foreign bodies in the maxillary sinus are presented. Four patients had iatrogenic foreign bodies, including a dental implant, a maxillary wisdom tooth, a maxillary wisdom tooth root and a dental root canal filler. The other two patients with non-iatrogenic foreign bodies fractured an interdental brush while cleaning their teeth and it entered the maxillary sinus. For surgical extraction of foreign bodies, the intra-oral and trans-nasal approaches were performed in 5 patients and 1 patient, respectively. A total of 130 Japanese patients with foreign bodies in the maxillary sinus from 1981 to 2015 were reviewed. The rate of iatrogenic and non-iatrogenic cases were 97.7%, and 2.3% respectively. With regard to dental foreign bodies, all of the reported patients had a tooth root in the maxillary sinus, and our patients with displacement of an entire tooth(including the crown and root)in the maxillary sinus was rare. It is necessary for dentists to perform detailed preoperative evaluation and careful extraction of maxillary wisdom teeth. There were 3 patients with broken interdental brush in the maxillary sinus. The common point of those 3 patients and our 2 patients was that relatively new interdental brushes were used, and been inserted into the periodontal pocket, which is an incorrect cleaning method. It is important for dentists and dental hygienists to provide instructions on the appropriate method of cleaning the teeth with interdental brush in order to prevent fracture and entry of the broken brush into the maxillary sinus
