1. INTRODUCTION In recent years, there have been positive trends in our country in increasing the effectiveness of endodontic dental treatment in connection with the introduction of modern technologies that allow predicting the results of dental treatment. However, in clinical practice, the number of failed treatment outcomes for caries complications has not decreased. It is known that the key to the effectiveness of endodontic treatment is the "three pillars": cleaning, sterilization and obturation of the root canal system. However, at every stage of endodontic treatment, a significant number of errors are obtained. So, according to the data of X-ray examination, it was found that only in 13.4% of cases the root canals were filled satisfactorily. But even with high-quality obturation, inflammation in the periodontium is observed in 5-8% of cases. The main mistakes that occur during endodontic treatment are: - perforation of the tooth; - breaking off an endodontic instrument or a post in the root canal; - poor quality passage and expansion of the root canal; - Poor quality filling (obturation) of the root canal. Errors of endodontic treatment can also be made at the diagnostic stage. The appearance of diagnostic errors is associated, among other things, with an insufficient frequency of X-ray examination.