Comparative evaluation of irrigation techniques on dentin nanohardness, flexural strength, and chemical composition:...

This investigation sought to evaluate the comparative influence of different irrigation activation protocols-ultrasonic, sonic, XP-Endo Finisher, and manual dynamic activation (MDA)-on the nanohardness, elastic modulus, flexural strength, and elemental composition of root dentin. Fifty intact single-rooted human mandibular premolars were decoronated 15 mm from the apex and instrumented using the ProTaper Next rotary file system (Dentsply Sirona, USA) under standardized irrigation protocols. Specimens were randomized into five groups (n = 10/group): ultrasonic activation, sonic activation, MDA, XP-Endo Finisher, and a non-activated control. Nanohardness and elastic modulus were measured, while flexural strength was evaluated using a three-point bending test. Elemental composition analysis was conducted with energy-dispersive X-ray spectroscop. Statistical comparisons were performed using one-way ANOVA followed by Tukey's HSD post hoc tests in SPSS v26 (IBM, USA), with significance set at p < 0.05. Statistical comparisons revealed statistically insignificant differences in nanohardness / GPa (F = 1.207, p = 0.321) and flexural strength / GPa (F = 0.808, p = 0.527) across groups. However, elastic modulus / MPa exhibited intergroup variation (p < 0.05), with post hoc Tukey's tests indicating higher values in the sonic activation group compared to ultrasonic activation and XP-Endo Finisher groups. EDS analysis showed no significant differences in oxygen, calcium, or phosphorus content (p > 0.05). Irrigation activation protocols had no significant effect on root dentin nanohardness, flexural strength, or elemental composition; however, sonic activation demonstrated a significantly higher elastic modulus. These findings highlight the mechanical stability of dentin across various activation methods.