An estimated 10% to 12% of cases involving maxillary sinusitis has historically been attributed to odontogenic infections. Conditions that may violate the Schneiderian membrane, such as periapical abscesses, periodontal disease, dental trauma, tooth extractions or placement of dental implants, are thought to increase the risk of maxillary sinusitis.Due to the close contact between the roots of the maxillary posterior teeth and maxillary sinus This article will illustrate, based on a relevant case, the relationship between periodontal disease and the pathologic changes of the Schneiderian membrane in the maxillary sinus, appropriate management, as well as the comparison of traditional radiography and computed tomography on interpreting the relationship between the roots of the maxillary posterior teeth and maxillary sinus. (J Taiwan Periodontol 16: 275-288, 2011)