en Dentistry پژوهشي Research <div style="text-align: justify;"><strong>Background and objectives:</strong> The developing process is necessary for converting a latent image into a visible image in conventional dental x-ray films. Despite the considerable advances made in development of radiographic equipment, there are also still some unresolved issues in this field. New self-developing film is an alternative to manual processing. The purpose of this study was to compare accuracy of self-developing films and conventional films (E-speed) for determination of the distance between file tip and radiographic apex in root canal therapy in laboratory conditions.<br> <strong>Methods:</strong> This study was done on 25 single-canal, single-rooted premolar teeth. After obtaining tooth length, each tooth was accessed and K-files No. 15 and 25 were placed inside the canal tip to tip with the tooth apex. Then, 1mm of the actual tooth length was reduced and periapical radiographs were captured using self-developing films and conventional films (E-speed) under standard conditions. Two endodontists observed the films twice at different intervals. The obtained data were analyzed with SPSS software (version 18) using paired t-test.<br> <strong>Results:</strong> Average distance between the tip of file No.15 to the radiographic apex in conventional film and self-developing film was 0.37 mm and 0.35 mm, respectively. The mean working length measured using K-file No. 25 was 0.44 mm in conventional film and 0.40 mm in self-developing film. There was no statistically significant difference between the two methods for measuring the working length.<br> <strong>Conclusion:</strong> The self-developing films provide a radiographic image that is diagnostically equivalent to the conventional film for measurement of the distance from the file tip to the radiographic apex in single-rooted teeth with a single canal.</div> Self-developing film, radiographic apex, conventional film 1 5 http://jcbr.goums.ac.ir/browse.php?a_code=A-10-76-19&slc_lang=en&sid=1 Parichehr Pourshakibaei پریچهر پورشکیبایی 10031947532846002049 10031947532846002049 No Dental Research Center, Golestan University of Medical Sciences, Gorgan, Iran Mohammad Taghi Mashkouri Najafi محمد تقی مشکوری نجفی 10031947532846002050 10031947532846002050 No Student Research Committee, School of Dentistry, Golestan University of Medical Sciences, Gorgan, Iran Amir Hossein Akbari Zahmati امیرحسین اکبری زحمتی 10031947532846002051 10031947532846002051 Yes Student Research Committee, School of Dentistry, Golestan University of Medical Sciences, Gorgan, Iran Mehrnoush Afiat مهرنوش عافیت 10031947532846002052 10031947532846002052 No Student Research Committee, School of Dentistry, Golestan University of Medical Sciences, Gorgan, Iran Masoumeh Vaghari 10031947532846002053 10031947532846002053 No Student Research Committee, School of Dentistry, Golestan University of Medical Sciences, Gorgan, Iran