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

Root canal irrigation is essential for effective canal disinfection, but activation techniques may alter the mechanical properties of root dentin.

To evaluate the effects of four different root canal irrigation techniques on root dentin nanohardness, elastic modulus, and flexural strength.

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).

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).

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.