Limewater combination therapy can reduce root canal endotoxins

By Sarah Guy

Treating root canals with a combination of chlorhexidine (CLX) gel and calcium hydroxide (0.14% limewater) results in significant reduction of endotoxins and neutralization of cytotoxic effects compared with the gel plus polymyxin B (PmB) or saline, report Brazilian researchers.

Endotoxins are the main virulence factor of Gram-negative bacteria, which have a known association between polymicrobial infection of root canals and clinical signs and symptoms including pain and edema, explains the team. Endotoxins exert various biologic effects resulting in the amplification of immune and inflammatory responses.

"Therefore, treatment of infected root canals should not only destroy bacteria but should also inactivate their endotoxins and other toxic products," suggest Luciane Dias de Oliveira (Universidade Estadual Paulista/UNESP, Saõ Paulo) and co-authors in the Journal of Endotontics.

The team treated 36 patients with root canal infection with either CLX + LW (n=12; 2% CLX gel + apyrogenic saline, followed by limewater), CLX + PmB (n=12; 2% CLX gel + apyrogenic saline, followed by PmB), or CLX (n=12; 2% CLX gel + apyrogenic saline).

Participants' root canals were sampled for evidence of endotoxins immediately after coronal opening (S1), after the biomechanical preparation was applied (S2), after flooding with ethylenediamine-tetra-acetic acid (S3), and after 14 days, when the intracanal medication was removed.

Using the chromogenic Limulus amebocyte lysate assay, the researchers observed endotoxins in 100% of S1 samples. However, at time point S2, endotoxin levels had reduced significantly in all treatment groups, and significantly more so in the CLX + LW group, at a 99.18% reduction, compared with a 90.78% fall in group CLX.

The authors report a slight, but nonsignificant increase in endotoxin levels at S3, but by S4, the reduction was significant reduction, with no significant differences between treatment groups.

"These results indicate that the use of limewater during the final steps of root canal instrumentation is feasible and has benefits for endodontic therapy, neutralizing most endotoxins after the death of gram-negative bacteria," write Dias de Oliveira et al.

Production of the cytokines interleukin (IL)-1β and tumor necrosis factor (TNF)-α, indicating immune and inflammatory response, was similarly high at S1 in all groups. By time point S2, IL-1β production was lower in all groups, and remained low, while TNF-α lowered at S2 but remained high.

These elevated levels indicate the sensitivity of TNF-α production to bacterial factors such as endotoxins, remark the researchers.

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