Zahra Tafakhori - Associate Professor, Department of Oral and Maxillofacial Radiology, Faculty of Dentistry and Dental Research Center, Rafsanjan University of Medical Sciences, Rafsanjan, Iran

and Objectives: The maxillary sinus is the first paranasal sinus to develop and its developmentends by 20 years of age. The topography of the sinus floor and its relationship with maxillary teeth roots varies with age, pneumatization size and grade, positioning of the teeth, and genetics. Therefore, this study used cone-beam computed tomography (CBCT) to evaluate the distance between posterior teeth and the maxillary sinus floor in patients from Rafsanjan (a city in Iran). Materials and Methods: This descriptive cross-sectional study evaluated 35 CBCT radiographs from patients over 20 years of age whoattendeda private oral and maxillofacial radiology clinic in Rafsnjan for dentistry procedures. The CBCT imaging was performed. After obtaining multi-planar reformatted (MPR) images,a maxillofacial radiologist measured the vertical relationships (the shortest distance) between the mesiobuccal, distobuccal, and palatal roots of posterior maxillary teeth and themaxillary sinus floor and classified them as described by Didilescu. The collected data were sequentially entered into SPSS21.0 .Results: In the second molars ofthe left region, the distances between the mesiobuccal, palatal, and distobuccal roots of the posterior teeth and the maxillary sinus floor were mostly type0. In the first molars of the left region, the distances between the distobuccal, palatal, and mesiobuccal roots and the maxillary sinus floor weremostly type1, 0, and 2, respectively. In the second molars of the right region, the distance between the maxillary sinus floor and mesiobuccal and distobuccal roots and palatal rootsweremainly type0 and type1, respectively. In the first molars of the right region, the distance between the maxillary sinus floor and mesiobuccal, palatal, and distobuccal roots was mostly type0. Generally, the distobuccal root of the second molars had the shortest distance from the maxillary sinus floor. Statistical tests showed no significant relationships between the measured distances and age, gender, or the assessed region.Conclusion: Since the distance between posterior maxillary teeth and maxillary sinus floor was mostly type0 in the population of Rafsanjan, clinicians are recommended to use CBCT to obtain adequate knowledge of the anatomy and morphological details of toothroots before any treatments, especially surgical procedures.