Object. Causes of failure of endodontic treatment and causes of tooth extraction with a diagnosis of chronic apical periodontitis. Purpose ― to analyze the causes of failure of endodontic treatment and the causes of tooth extraction with a diagnosis of chronic apical periodontitis to determine ways to improve the effectiveness of conservative treatment. Methodology. A retrospective analysis of 864 medical records of a dental patient and 532 results of x-ray examinations of patients who underwent tooth extraction was carried out. 198 dentists-therapists of the city of Tyumen and the South of the Tyumen region were interviewed to determine the shortcomings of endodontic treatment. During the survey, doctors expressed their subjective opinion about the main reasons for the failure of therapeutic treatment of teeth with apical periodontitis and the reasons for their subsequent tooth extraction. Results. According to the survey, the failure of conservative treatment is most often associated with non-compliance with treatment protocols and the complexity of the anatomical structure of the root canals, as well as the inability to adequately clean the root canal system. A retrospective analysis of the data related to tooth extraction revealed that the main cause of tooth extraction is chronic apical periodontitis, which accounts for 69 %. The main reason for the removal of teeth diagnosed with chronic apical periodontitis was a significant destruction of the crown. Summary. In the course of this work, we justified the need to improve existing methods of conservative treatment of apical periodontitis. Improvement of endodontic treatment should be aimed at the development and implementation of effective methods of root canal cleaning and irrigation solution activation. In order to improve the prognosis of endodontic treatment and reduce the proportion of tooth extractions for periodontitis, it is necessary to improve the quality of the final restoration and to monitor its tightness.

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A device and techniques for vacuum-bolus irrigation of root canals are developed on the basis of the analysis of existing methods of medical treatment of root canals in endodontic treatment. A comparative assessment of the impact of different variables of vacuum on the degree of cleaning of the root canal model was carried out in an invitro experiment and the optimal values of vacuum and exposure time were pointed out. In the clinical part of the study 52 patients aged from 25 to 44 years with a diagnosis of apical periodontitis were treated and dynamically monitored during one year (the author`s vacuum-bolus technique was applied to 32 patients of the main study group in the course of endodontic irrigation of root canals; while 20 patients of the control group experienced a standard irrigation method with the use of endodontic syringe in the course of endodontic treatment). Criteria of the modified periapical index (PAI) were used to assess the efficacy of treatment. It was found that after 12 months, 90,5 % of patients of the main study group had no signs of demineralization of bone tissue, the orientation of bone trabeculae of cancellous bone and cortical plate were recovering. Thus, the vacuum-boluc irrigation of root canals can help us improve the efficiency of treatment of destructive forms of apical periodontitis.