Impact of Ethylenediaminetetraacetic Acid, QMix, and Citric Acid Solutions on Root Dentin Nanohardness and Flexural Strength: An In Vitro Study

Aim: This research investigated the distinct irrigation protocols: 17% ethylenediaminetetraacetic acid (EDTA), QMix, 40% citric acid on the mechanical properties of root dentin, particularly, nanohardness, and flexural strength.Materials and methods: Forty sound single-rooted mandibular premolars extracted for orthodontic or periodontic reasons were selected.The canals were mechanically prepared using ProTaper Next rotary instruments.Each root was longitudinally bifurcated into two halves; one was designated for nanohardness measurement, while the other was processed into a dentin bar for flexural strength testing.Both sample sets (n = 10 per group) were then randomly allocated into four study groups.In group I: 5 mL of EDTA was used for 2 minutes and then flushed with saline.Similarly, groups II, III, and IV used QMix, 40% citric acid, and normal saline (control).The nanohardness was measured using a nanoindenter with a Berkovich diamond tip.Flexural strength was evaluated via a three-point bending test.The obtained data were statistically analyzed using a one-way analysis of variance (ANOVA) test and a post hoc multiple comparison test, with a significance level set at 5%.Results: The control group exhibited the highest mean nanohardness at 0.49 ± 0.06 GPa, whereas the 17% EDTA group showed the lowest mean at 0.28 ± 0.07 GPa, representing a statistically significant difference (p < 0.05).A similar trend was observed for flexural strength, with the control group reaching 108.5 ± 23.8 MPa and the 17% EDTA group exhibiting the lowest strength at 55.9 ± 23.6 MPa.Overall, 17% EDTA significantly reduced both nanohardness and flexural strength compared with all other study groups (p < 0.05). Conclusion:The mechanical properties of dentin were significantly influenced by the choice of irrigant, with both nanohardness and flexural strength following a descending order of normal saline > QMix > citric acid > EDTA.These findings indicate that while all tested chelating agents impacted the tooth's structural integrity, 17% EDTA exhibited the most deleterious effect on the mechanical properties of root dentin compared with the other groups.Clinical significance: Choosing an appropriate irrigant is vital for preserving the tooth's structural integrity.Since 17% EDTA significantly reduces nanohardness and flexural strength, using alternatives like QMix or citric acid may better maintain the mechanical properties of dentin and reduce the risk of posttreatment root fractures.