Evaluation of the effect of digital magnification on the accuracy of endodontic file length determination

Considering the application of magnification in evaluation of digital images during root canal therapy to assess the tip of small endodontic files، the purpose of the present study was to evaluate measurement accuracy of endodontic file lengths in periapical digital radiography after using digital magnification tools. In this experimental study، thirty-five human single rooted permanent teeth with 20‒24 mm of canal length were selected. ISO #08 endodontic files were placed in the root canals up to the working length. The files lengths were measured with digital caliper as gold standard. Periapical digital images were obtained with Digora storage phosphor plates and their special scanner، Digora Optime، using a Prostyle dental X-ray unit as original images. Magnification tools were applied to each original image. Two blind radiologists measured the file lengths on original and magnified images. The measurements were compared using ANOVA and Bonferroni test (α=0. 05). All the digital images with and without magnification overestimated file lengths in comparison to the gold standard (p value = 0. 45). Measurement accuracy of ×2 and ×3 magnified images did not show any significant differences in comparison to original digital images (p value = 1 and p value = 0. 44، respectively). There was no significant difference between ×2 and ×3 magnification (p value = 0. 15). Images with ×3 magnification overestimated measurements compared to original digital images; however، the differences were not significant (p value = 0. 10). Under the limitations of the present study and based on the results، use of magnification tool did not influence length measurement accuracy of small endodontic files on digital periapical radiographs in vitro.