The present study investigated the position and relationship of the maxillary third molars to the maxillary sinus. These molars were detected to have a close relationship with the maxillary sinus based on panoramic images, using cone-beam computed tomography (CBCT). This retrospective study evaluated 162 impacted third molars from 100 patients that showed a superimposed relationship between the maxillary sinus and third molars on panoramic images obtained from CBCT. CBCT images were used to assess the horizontal (buccopalatal) and vertical positions of the maxillary sinus relative to the maxillary third molars, proximity of the roots to the sinus, and angulation and depth of the third molars. The associations among the angulation, depth of third molars, and horizontal and vertical positions of the maxillary sinus relative to the third molar findings were examined using Chi square tests. Based on the winter classification, the most frequent tooth position was vertical (59.9 %), followed by mesioangular (14.2 %), distoangular (9.9 %), and others. Most impacted teeth were at the level between the occlusal and cervical levels of the adjacent second molar. Regarding the relationships of the maxillary third molars with the maxillary sinus examined on CBCT, vertical type III (buccal root related with maxillary sinus) (34 %) and horizontal type 2 (maxillary sinus located between roots) (64.8 %) were seen most frequently. The relationship between the maxillary sinus and third molar roots should be considered during extraction. When a risk of sinus perforation is predicted in an extraction, a presurgical CBCT examination could be valuable.
