RESUMO
Objective To study the morphological variations of maxillary sinus and to provide anatomical basis for maxillary posterior teeth implantation and extraction usingcone-beam computed tomography (CBCT) scan-ning. Methods CBCT images from 403 patients were reviewed. The minimal distance from sinus floor to alveolar ridge wasmeasured and the number of patients with clinical features such as having sinus septum , mucosal thicken-ing and posterior teeth roots extend into maxillary sinus were counted. Results The mean value of the minimal dis-tance from maxillary sinus floor to alveolar ridge was about 8.3 mm, there was no significant statistical difference between sex, but there was a significant statisticalsignificant difference between the left sides and the right sides. Occurrences of sinus septum, mucosal thickening and roots into sinus were 98.6%, 31% (in which 56.3% of mu-cosal thickening were related to apical periodontitis) and 47%. there was no significantstatisticaldifference between the two sides in males females. Conclusions The morphological variations of maxillary sinus are significant. Chron-ic inflammation in maxillary sinuis is closely related to the position of maxillary posterior teeth roots and periapical lesions.