Roentgenographic in vitro investigation of frequency and location of curvatures in human maxillary premolars

The aim of this study was to determine the location of the root canal curvature and measure the distance from the CEJ to the first curvature using in vitro methods. Extracted maxillary premolars (n = 358) were fixed and digitally radiographed using the parallel technique. Excluded from further analysis were teeth with root caries, artificial crowns, extensive fillings, or endodontic treatments. The results were descriptively analyzed and the cumulative frequencies were calculated. The median values of the distance between CEJ and first curvature were for the first right premolars 8.4 mm (buccal) and 8.5 mm (palatal), for the first left premolars 9.1 mm (buccal) and 8.9 mm (palatal). The median distances in the second premolars were 10.7 mm (right side) and 10.2 mm (left side). The results showed that a high number of maxillary premolars had a curvature with a median value of 8 mm apically from the CEJ. Our findings suggest that such measurements may be useful to consider during endodontic treatment and post insertion.