Endodontic treatment of teeth characterized by a complex anatomy of root canals is an urgent problem of modern dentistry. This article compares the immediate and long-term results of treatment of curved root canals using the sound method of activation of irrigation solution and the standard method of treatment, in which the activation of the solution was not carried out. The purpose of the study: to increase the effectiveness of endodontic treatment of root canals with complex anatomy by using sound methods. Materials and methods: Molars and premolars were examined and treated in 50 patients aged 25-44 years with a diagnosis of chronic apical periodontitis (K 04.5). The diagnosis was established on the basis of basic and additional research methods. The patients underwent diagnostic CBCT before treatment, as well as 6 and 12 months after treatment. The main group consisted of 25 patients in whom sound activation of a 3% sodium hypochlorite solution was used in the treatment of root canals at the stage of final root canal treatment, the control group consisted of 25 patients who used a standard technique of root canal irrigation from an endodontic syringe. Endodontic treatment in patients of both groups was carried out according to the standard protocol of root canal treatment. Mechanical processing was carried out with manual endodontic instruments, and then with machine Ni-Ti files. Drug treatment was carried out with 3% sodium hypochlorite solution and 17% EDTA solution. During the first visit after mechanical and medical treatment, the root canals of patients of both groups were temporarily obstructed with calcium-containing paste "Calasept". Permanent obturation of the root canal was carried out by the method of lateral condensation of gutta-percha, a material based on epoxy resins "AH plus" was used as a siler. As a result of the study, it was revealed that the patients of the main group did not complain in the next 3-7 days after the end of treatment. Dental percussion and mucosal palpation were painless in 23 patients. Slightly pronounced mucosal hyperemia and discomfort during palpation in the projection area of the root tips along the transitional fold were determined in 2 patients. In the control group of patients, during the first 7 days after permanent obturation of the root canals of the teeth, 5 people had pain when biting on the tooth, painful percussion and hyperemia of the mucous membrane in the projection of the root tip of the treated tooth. The remaining 20 patients had no complaints. The analysis of radiographs revealed that 12 months after treatment in patients of the main group, a decrease in the size of periapical foci of bone destruction was noted in all 25 teeth. In 23 teeth there was a complete restoration of the bone structure in the periapical foci, which was 92%, and in 2 teeth there was a partial restoration of the bone structure (6%). The condition without changes in the periapical tissues, or an increase in the focus of bone destruction in patients of the main group 12 months after treatment, we have not been detected. When analyzing radiographs in patients of the comparison group in 19 (76%) teeth there was a complete restoration of the bone structure in the periapical region and in 5 (20%) teeth there was a partial restoration of bone tissue from the teeth. In 1 (4%) tooth, foci of bone tissue destruction were determined on radiographs, the size of which remained unchanged. Thus, the use of a sound method of activating a 3% sodium hypochlorite solution in teeth with a complex root canal anatomy at the stage of finishing irrigation makes it possible to effectively clean the root canal from the lubricated layer, which contributes to high-quality root canal obturation and a significant reduction in immediate and long-term complications after treatment.