•Purpose: to determine the length of the straight line between CEJ and the beginning of the first curvature in maxillary premolars, and the distances between the first and second curvatures from radiographic apex including the curvature degree determination.
•N= 358 extracted maxillary premolars
•Inclusion criteria: teeth with a definable CEJ, clinical crowns and apex. •Exclusion criteria:, teeth with root caries, crowns or extensive fillings and type II and type IV root canal configurations, second premolars with two root canals.
•Sample was selected and fixed with a special fixation device.
•Digital radiographs were obtained in a bucco-lingual plane using the parallel technique.
•A horizontal line between the mesial and distal CEJ served as the coronal reference level.
•A number of points, lines and angles were defined and located on each radiograph corresponding to the CEJ, 1st and 2nd canal curvatures and the apex.
•A descriptive statistical analysis was carried out (frequencies, mean and median ).
Most highlighted Results:
•The mean value of distance between CEJ and first curvature were 8.7 mm of the maxillary first premolars, and 10.4 mm for the maxillary second premolars.
these measurements are useful during endodontic treatment to avoid ledges formation or perforations, and in restorative treatments such as post insertion.