Abstract: Objective To measure and analyze the positional relationship of maxillary posterior tooth roots and their adjacent anatomical structures in order to provide references for clinical treatment. Methods One hundred and twenty cases which met the inclusion criteria were chosen from CBCT database of Stomatology Hospital of Shandong University. GALAXIS software was used to observe the classification of the relationship between the posterior maxillary tooth roots and the maxillary sinus floor, and to evaluate the incidence of various types. The vertical distance from the roots apical to the bottom of the maxillary sinus and the horizontal distance from root midpoint to the adjacent alveolar bone plate were measured and statistical analysis was carried out. Results The type that root apical and maxillary sinus was separated by bone plates had the highest incidence. The mesiobuccal root of maxillary second molar had the shortest vertical distance to the maxillary sinus (P<0.05); the palatal root of maxillary second premolar and second molar had the longest vertical distances to the sinus floor (P<0.05). The first molar mesiobuccal root was nearest to the buccal bone plate (P<0.05), and the first molar palatal root was nearest to the palatal bone plate (P<0.05). Conclusion Posterior maxillary tooth roots have a close relationship with the sinus floor and the alveolar bone plate, which should be noted in the clinical treatment. CBCT can show the relationship of posterior maxillary tooth roots and their adjacentanatomical structures clearly, and is suitable for accurate diagnosis and design before treatment.

Key words: Cone-beam CT, Maxillary posterior teeth, Maxillary sinus, Anatomical relationship