Foreign Body in the Maxillary Sinus Identified by MRI

We report a case of a foreign body in the maxillary sinus, in which magnetic resonance imaging (MRI) was useful in reaching the diagnosis. The patient was a 37-year-old man, who presented at our hospital with fever and a headache after he had received dental treatment in a local dental clinic. The symptoms were suspected to be due to migration of a piece of agar impression material, which was used for the dental treatment, into the maxillary sinus; however, a computed tomography scan did not show the foreign body clearly. Using MRI, we were able to distinguish the material from hypertrophic mucous membranes in the maxillary sinus. In addition, we performed another MRI of the impression material itself to compare with the MRI of the patient, which suggested the strong possibility of migration of the impression material into the maxillary sinus.