Effectiveness of Continuous and Sequential Chelation and Different Agitation Techniques on Smear Layer Removal and Microhardness of Root Canal Dentin

Systematic reviews and original research articles should have a structured ab-stract of around 250 words and contain the following headings: Background/Objectives, Methods, Results, and Conclusions. Background/Objectives: This study aimed to assess and compare the elimination of the smear layer and microhardness of dentin in root ca-nals after sequential versus continuous chelation using different agitation techniques. Methods: Sixty-four palatal roots of upper first molars were instrumented to size X3 (Protaper Next files). According to the irrigant solution, samples were assigned to two groups (N=32/group), 3% NaOCl irrigation followed by 17% EDTA (sequential chelation (SC)), or Dual Rinse (3% NaOCl/9% HEDP) irrigation (continuous chelation (CC)). Each group has been divided into four subgroups (n=8/subgroup), based on agitation tech-niques used: conventional needle (CN)(control group), EndoActivator (EA), ultrasonic ag-itation (UAI), and Er.Cr.YSGG 2780 nm (laser). SEM images assessed the smear layer, and Vicker microhardness (VHN) was performed at 50 and 100 µm depths. Data was ana-lyzed using: Kruskal-Wallis, Wilcoxon, and Mann-Whitney U test. Statistical significance was set at p< 0.05. Results: In the UAI and laser agitation, CC significantly reduced the smear layer presence compared to SC in the apical and coronal thirds, respectively (p< 0.05) and no significant differences were observed in the CN and EA groups between SC and CC (p>0.05). There were significantly higher VHNs of dentine in CC groups than in SC groups in all sections and depths except in the apical of the CN group at 50 µm and the coronal section of EA and UAI groups at 100 µm. Conclusions: CC was comparable to SC in smear layer removal. CC had a less detrimental effect on dentin compared with SC.