Endotoxin Levels after Calcium Hydroxide Placement in Root Canals Irrigated with Continuous or Sequential Chelation in Previously Treated Teeth with Symptomatic Apical Periodontitis: A Randomized Controlled Clinical Trial.

Introduction: Endotoxins are proinflammatory components of Gram-negative bacteria. The aim of this randomized clinical trial was to test the null hypotheses that (i) there is no significant difference between continuous chelation irrigation (5.25% sodium hypochlorite + 9% etidronic acid) and sequential chelation (5.25% sodium hypochlorite - 17% ethylene diaminetetra-acetic acid) in endotoxin reduction, and (ii) placement of calcium hydroxide (CH) does not further improve endotoxin reduction in previously treated teeth with symptomatic apical periodontitis.

Methods: Previously treated teeth with symptomatic apical periodontitis (n = 48) were randomly allocated to (n = 24) Group 1, sequential chelation (SC) or Group 2, continuous chelation (CC). Root canal sampling was performed with sterile paper points at three time intervals: immediately after gutta-percha removal (T₀), following chemomechanical preparation (T₁), and following 7 days of CH placement (T₂). A turbidimetric kinetic limulus amebocyte lysate assay was used for endotoxin quantification. Repeated measures ANOVA was used to compare SC and CC at different time points and between different time points for each protocol. P < .05 was considered to be statistically significant.

Results: Both SC and CC showed significant endotoxin reduction from T₀ to T₁ (P < .05), while only SC group exhibited further significant reduction from T₁ to T₂ (P < .05). CC group demonstrated significantly lower endotoxin levels than the SC group at T₁ (P < .01) and T₂ (P < .001).

Conclusion: This study shows for the first time that CC irrigation resulted in significantly lower quantity of endotoxins than SC followed by calcium hydroxide.