Accessory ostium, also referred to as accessory sinus ostium or just sinus ostium, are a common anatomical variation in humans. However, they may be due to a sinusal disease.They are described as bony dehiscences that are covered with mucosa that allow nasal fluids to leak into other areas of the sinus. Despite this, no connection has been found between the presence of accessory ostium and the increase in rhinitis or sinusitis symptoms in patients who have them. The cause of accessory sinus ostium may also be attributed to maxillary sinusitis, obstruction of the primary ostium, or anatomical or pathological abnormalities in the middle meatus. These conditions may cause the rupture of membranous areas, resulting in accessory ostium. Knowledge of the structures within the maxillary sinus is important in determining whether the patient will need a bone graft prior to the implant. In rare cases, implant hardware can become displaced in the sinus cavity.