Endodontic treatment is based on two complementary principles: mechanical and chemical preparation of the root canal system. Studies have demonstrated that endodontic instruments are capable of preparing only approximately 65-80% of the root canal wall surface, with the remaining substantial portion of the canal system insufficiently cleaned. Chemical canal preparation involves irrigation with specific solutions, such as sodium hypochlorite (NaOCl), ethylenediaminetetraacetic acid (EDTA), and chlorhexidine, which facilitate the dissolution of organic debris, eliminate microorganisms, and remove the smear layer. The aim of the study was to evaluate the effect of sodium hypochlorite on the mechanical properties of teeth subjected to root canal irrigation with 5.25% NaOCl, and to analyze microstructural and chemical changes- specifically shifts in the elemental composition of root dentin exposed to sodium hypochlorite. Human teeth extracted for orthodontic reasons, including canines and first premolars with single root canals, were used as the study material. Five premolars and five canines were used as control groups, and five premolars and five canines were used in the study groups. Teeth with similar root and crown dimensions were selected. The specimens were randomly assigned to two groups: a control group consisting of teeth not exposed to 5.25% NaOCl and an experimental group comprising teeth irrigated with 10 ml of sodium hypochlorite in three cycles, each lasting four minutes. The samples were subsequently subjected to failure load testing, microstructural analysis, and elemental composition assessment using energy-dispersive X-ray spectroscopy (EDS). In addition, statistical analysis was performed using the Shapiro-Wilk test. Based on the results obtained in the present study, the following conclusions can be drawn that he strength properties of teeth subjected to root canal irrigation with 5.25% NaOCl were lower in both test groups compared to the control groups, in which physiological saline was used as the irrigant. Additionally, EDS analysis of changes in the elemental composition of root dentin treated with 5.25% NaOCl revealed alterations in calcium and phosphorus content following exposure, accompanied by a reduction in the force required to fracture the teeth. Above the authors highlight the need for further research using EDS spectroscopy to determine the cause-and-effect mechanism linking failure load to elemental changes in root canals irrigated with 5.25% NaOCl.