Effect of Various Root Canal Irrigation Techniques on Root Dentin Mechanical Properties: An In Vitro Study.

BACKGROUND: Root canal irrigation is essential for effective canal disinfection, but activation techniques may alter the mechanical properties of root dentin. OBJECTIVE: To evaluate the effects of four different root canal irrigation techniques on root dentin nanohardness, elastic modulus, and flexural strength. METHODS: Forty extracted human mandibular premolars with single straight canals were randomly allocated to four groups (n = 10): traditional needle irrigation, passive ultrasonic irrigation (PUI), negative-pressure irrigation, and XP-Endo Finisher irrigation. During canal preparation, specimens were irrigated with 1% sodium hypochlorite. The final irrigation procedures were performed using 2.5% sodium hypochlorite and 17% EDTA with identical irrigant sequences and volumes across all groups. Root dentin nanohardness, elastic modulus, and flexural strength were evaluated. Data were analyzed using one-way ANOVA and Tukey's post hoc test (p < 0.05). RESULTS: Traditional needle irrigation demonstrated the highest nanohardness (0.489 ± 0.064 GPa), whereas ultrasonic irrigation showed the lowest values (0.391 ± 0.021 GPa). Negative-pressure irrigation (0.466 ± 0.043 GPa) and XP-Endo Finisher irrigation (0.436 ± 0.056 GPa) showed intermediate values. Elastic modulus did not differ significantly among the groups (p = 0.148). Likewise, no significant difference in flexural strength was observed among the irrigation protocols (p = 0.371). CONCLUSION: Under the conditions of this in vitro study, ultrasonic irrigation reduced dentin nanohardness, whereas neither elastic modulus nor flexural strength was significantly affected by the irrigation protocol.