A total of 21 root canals with pulp necrosis and apical periodontitis were analyzed by the three different LAL methods. All three LAL methods were effective in the recovery of endotoxin from root canal infection. Regardless of the method

tested, endotoxin was detected in 100% of the root canals investigated (21/21). The KQCL assay yielded a median value of endotoxin of 7.49 EU/mL, which selleck compound was close to and not significantly different from the turbidimetric test (9.19 EU/mL) (both kinetic methods) (p > 0.05). In contrast, the endpoint QCL showed a median value of 34.20 EU/mL (p < 0.05) ( Table 2). The percentage of PPC values revealed a good interaction between the root canal samples and LAL substrate regarding the turbidimetric method (% values ranging from 50 to 197) (Table 2). Product inhibition values were found in 2 of 21 root canal samples analyzed by the KQCL method (PPC value <50%). The endpoint QCL revealed product interference in 12 of 21 root canal samples (values lower than 0.4 EU/mL ± 25%)

(Table 2). The color interference assay performed for the endpoint-QCL method indicated color interference in 11 of 21 root canal samples, even after a dilution to the 10−4. The linearity of the standard curve was equally good for all methods (all r =1) ( Table 2). The coefficient of variance for endotoxin concentration was greater than 10% in 17 Selleck LBH589 of 21 root canal samples analyzed by the endpoint-QCL assay, indicating its low reproducibility ( Table

2). In contrast, the KQCL and turbidimetric kinetic assays revealed as high as 5.50% and 4.46% values of the coefficient of variance, respectively (both being precise and with best reproducibility) ( Table 2). The LAL tests use a serine protease catalytic coagulation cascade that is activated Ribonucleotide reductase by endotoxin (18). Factor C, the first component in the cascade, is a protease zymogen activated by endotoxin binding. Downstream, this pathway activates a proclotting enzyme into a clotting enzyme (coagulogen into coagulin) (18). The chromogenic LAL assay (QCL or KQCL) uses the synthetic peptide-pNA substrate, which is cleaved by the clotting enzyme, imparting a yellow color to the solution. The turbidimetric kinetic assay uses coagulogen by monitoring its conversion into coagulin, which begins to form a gel clot, increasing the turbidity. The strength of the yellow color (determined at an optical density [OD] = 405 nm) resulting from the chromogenic LAL substrate and the turbidity (determined at an OD = 340 nm) resulting from the coagulogen conversion are correlated with the endotoxin concentration. The progress of the LAL reaction leading to coagulogen conversion (as measured by OD) was monitored in two ways in the current study: using the endpoint and kinetic methods. In the first (QCL test), OD is recorded at single time (≈16 minutes), which compromises its sensitivity (0.1-1 EU/mL) (18).