Assessment of Variations of The Number of Roots &Amp; Root Canal Configurations of Maxillary Premolars and Their Relation to the Floor of the Maxillary Sinus

Inclusion Criteria: * Fully maturated and erupted maxillary permanent premolars of Egyptian patients, males or females. * Intact maxillary premolars' roots without fractures or cracks. * Maxillary Premolars without posts or previous root canal treatment. * CBCT scans of different fields of view could be included as long as it shows maxillary premolars. * CBCT scans of 0.2 mm voxel resolution {the maximum voxel size accepted for endodontic imaging} Exclusion Criteria: * Maxillary premolars with: Developmental anomalies. External or internal root resorption. Root canal calcification. Previous root canal treatment Post restorations. Root caries especially reaching the bifurcation area. * Evidence of apicectomy or periapical surgery * CBCT images of poor quality or artifacts interfering with the assessment of the root canals.