Monitoring Host-Immune Response in Asymptomatic and Symptomatic Primary Endodontic Infections

Objectives: The objectives were 1) to identify microorganisms from root canals (RC) of asymptomatic teeth (AT) with pulp necrosis and periapical lesions, and from symptomatic teeth (ST) with periapical abscesses, and 2) to quantify LPS[bp1] , cytokines, metalloproteinases (MMPs) and Substance P (SP) levels at the different phases of the RC treatment (RCT), correlating them with clinical features.
Methods: The experimental groups (ExpGr) consisted of patients with AT (n=10) and ST (n=10). A control group consisted of patients requiring RCT of vital teeth due to prosthetic reasons (n=6). Microbiological/LPS samples were collected before chemomechanical preparation (CMP), after CMP and after 30 days of intracanal medication (ICM). Biomarker (BM) samples, including IL-1α, IL-1β, TNFα, PGE-2, MMP-2, MMP-3, MMP-8, MMP-9, MMP-13, and SP were collected 2mm beyond the apex after CMP/ICM. Microbiological samples were processed by NGS technique using MiSeq. LPS was analyzed by LAL assay. BMs were quantified using Multiplex kits. Friedman/Wilcoxon tests compared LPS and BMs levels at each clinical time; Spearman's test correlated LPS with BMs; multiple logistic regression correlated LPS/BMs with clinical features; p-values were set at 0.05.
Results: Microbiological comparisons between AT and ST presented differences (p=0.007). The most predominant phyla detected in both ExpGr were Firmicutes and Proteobacteria. Fusobacteria and Spirochaetes were found only in ST, while Actinobacteria was detected only in AT. Significant LPS reduction after CMP was obtained in both ExpGr (p<0.05), but after ICM only in ST (p<0.05). All BMs showed reduction after ICM (p<0.05). Greater LPS/SP levels were associated with tenderness to percussion and pain on palpation (p<0.05).
Conclusions: It was concluded that asymptomatic and symptomatic primary endodontic infections present differences in RC microbial profiles. CMP was able to reduce LPS in both cases. ICM for 30 days played an important role in LPS reduction in ST, which may have favored the restoration of physiological levels of BMs.