Infection in the maxillary sinus, either acute or chronic in nature, which can be caused by dental pathology, such as root tips, periapical lesions, overfilled endodontic material, and oroantral fistulae or openings, among others. Acute sinusitis is an absolute contraindication for surgery, whereas chronic sinusitis is a relative contraindication where implant and/or sinus floor elevation procedures may still be performed.