Purpose: New solutions are needed to overcome the disadvantages of irrigation solutions that are fre- quently used to remove the inorganic part of the smear layer. The goal of the current study was to compare the effect of 5%, 10%, and 17% GA, 9% HEBP, 17% EDTA, and 10% CA on the fracture strength of endodontically treated premolars.

Methods: Eighty-eight mandibular premolar teeth were selected. Eleven intact specimens were pre- served as negative controls. After root canal preparation, the specimens were divided into 8 groups for the final irrigation procedure: Positive control (distilled water), 17% EDTA, 10% CA, 9% HEBP, 5% GA, 10% GA, and 17% GA (n = 11). After the final irrigation procedure, the root canals were obturated. Access cavities were filled with composite resin. A universal testing machine was used to measure the force required to fracture the specimens. Data were statistically analyzed.

Results: The negative control group showed higher fracture strength than all other groups except the positive control group (p < 0.05). There was no statistically significant difference among the EDTA, CA, HEBP, and GA groups (p > 0.05).

Conclusion: Within the limitations of this study, 1-minute use of 17% EDTA, 10% CA, 9% HEBP, 5% GA, 10% GA, and 17% GA as final irrigation solutions, in combination with NaOCl, had no effect on the frac- ture resistance of premolar teeth.