In the course of the present study four endodontic treatment schemes were tested and the most effective scheme was determined through the use of calcium hydroxide-based paste being applied three times at an interval of 7—14 days with the subsequent long-term temporary obturation using calcium hydroxide with iodoform, ultrasonic activation of sodium hypochlorite in the root canal, hydrodynamic irrigation and a diode laser. During the entire treatment period, the most effective scheme has revealed a reduction in defect size by 2,57±0,17 (p>0,0001) as well as a 1,84 degree (p>0,0001) decrease in PAI score. Based on optical density data, it was concluded that the application of calcium hydroxide with iodoform in the treatment scheme leads to an 2,2—4,2% improvement in bone tissue regeneration in the periapical zone. The greatest and complete inhibition of microorganisms was determined in patients of the first and third experimental groups in which a diode laser was used. The use of a diode laser in endodontic dental treatment with periapical destruction, enhances antibacterial activity and contributes to the complete inhibition of pathogenic microflora in the root canals.