The effects of sequential and continuous chelation on dentine tubule penetration of a bioceramic sealer: A confocal laser scanning microscopy study

Objective: This thesis aims to evaluate the penetration of a bioceramic sealer into dentin tubules when activated with three different irrigation activation techniques [Conventional Syringe Irrigation (CSI), Passive Ultrasonic Irrigation (PUI), and XP-endo Finisher (XPF)] using two different sequential chelating agents [Ethylenediaminetetraacetic Acid (EDTA) and Glycolic Acid (GA)], and a continuous chelating agent, Dual Rinse HEDP. Materials and Methods: This study included 99 extracted intact human mandibular premolar teeth. They were divided into three main groups according to the irrigation regimen and three subgroups according to the activation type. The main groups were Group 1: Sodium hypochlorite (NaOCl) + EDTA (17%) (n=33), Group 2: NaOCl + GA (17%) (n=33), and Group 3: NaOCl and Dual Rinse HEDP mixture (n=33). The subgroups were: Group a: CSI (n=33), Group b: PUI (n=33), and Group c: XPF (n=33). In Groups 1 and 2, the irrigation regimen consisted of 15 ml of 5% NaOCl followed by 5 ml of the chelator, while in Group 3, to equalize the solution volume, Dual Rinse HEDP was used in combination with 20 ml of 5% NaOCl. Samples were rinsed with 5 ml of distilled water and dried with paper points. The teeth were embedded in acrylic using plastic molds. They were then filled using AH Plus® Bioceramic sealer with the single cone technique. Horizontal sections of 1 mm thickness were taken from the apical and middle regions and examined under a confocal microscope for penetration depth, percentage, and area. Data were analyzed using the Shapiro-Wilk test and three-way Robust ANOVA test. Results: According to the main effects of activation type and solution, there was no significant difference in penetration depth, percentage, and area among the groups (p>0.05). Regarding the main effect of the section, penetration parameters in the apical section were significantly less than those in the middle section (p=0.001). Examining the interaction of activation type and solution, the EDTA-CSI and Dual Rinse HEDP-XPF groups showed less penetration depth than the XPF-EDTA group (p=0.024). The highest mean penetration area was in the GA-PUI group, while the lowest was in the EDTA-CSI group (p=0.005). No statistically significant differences were observed in the three parameters measured among groups in the activation type-section and solution-section interactions (p>0.05). In the interaction of activation type, solution, and section, the highest penetration depth was found in the Dual Rinse HEDP-CSI-Middle section group, and the lowest was in the EDTA-PUI-Apical section group (p=0.029). The highest penetration percentage was in the Dual Rinse HEDP-XPF-Middle section group, and the lowest was in the Dual Rinse HEDP-CSI-Apical section group (p=0.041). The highest penetration area was obtained in the GA-PUI-Middle section group, while the lowest values were found in the GA-CSI-Apical section and Dual Rinse HEDP-PUI-Apical section groups (p=0.042). Conclusion: Continuous chelation protocols applied under different irrigation activation systems did not show superiority over traditional sequential chelation protocols regarding bioceramic sealer penetration. The activation system is an essential variable in selecting the chelation protocol to be applied. Chelator and activation combinations were insufficient in the apical region. Keywords: Continuous chelation, sequential chelation, sealer penetration, confocal laser scanning microscope, irrigation activation.