Comparison of endotoxin levels in previous studies on primary endodontic infections

This study was performed to determine which of the quantitative methods, namely, chromogenic endpoint, chromogenic kinetic, and turbidimetric kinetic ones, best fit for the analysis of primary endodontic infections.

Twenty-one root canals with apical periodontitis were sampled with paper points. The same sample was analyzed by means of the endpoint chromogenic Limulus amebocyte lysate (LAL) assay (QCL), quantitative kinetic chromogenic LAL assay (KQCL), and kinetic turbidimetric LAL assay (Turbidimetric).

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 (21/21). The KQCL assay yielded a median value of endotoxin of 7.49 EU/mL, close to and not significantly different from those for 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). The comparison of the three methods revealed that both turbidimetric and KQCL methods were more precise, with best reproducibility (the coefficient variation between analysis of the root canal and its duplicate was lower than 10%). The inhibition/enhancement assay indicated a good interaction between the root canal samples with the turbidimetric method.

This study has revealed that quantitative kinetic-turbidimetric and kinetic-chromogenic LAL methods are best fitted for the analysis of endotoxins in root canal infection, both being more precise and allowing better reproducibility compared with the endpoint-QCL assay.