The aim of this study was to evaluate the effects of exposing dental implants to the maxillary sinus cavity. This is a retrospective study. Thirteen patients with 18 implants that had radiographic evidence of implant exposure to the maxillary sinuses participated in this study. We evaluated the patient's radiographs immediately after implant insertion and 12 months after operation with the patient's clinical signs and symptoms due to sinusitis. Thirteen patients with 18 implants in the maxillary sinus had no signs and symptoms of sinusitis. Radiography showed thickening of the sinus membranes in 2 patients. All penetrated implants were successfully integrated, and there were no radiographic signs of bone loss or other complications.The exposure of implants to the maxillary sinuses caused no problems in the maxillary sinuses, and bone formation occurred in THE maxillary floor when penetration of maxillary sinuses occurred without tearing of the membrane.