Think outside the canal: Systemic health considerations of apical periodontitis and the endodontic microbiome

Apical periodontitis (AP) is the outcome of host-microbiome interaction at the root-apex. The effect of this interaction on the immune system, translated into changes in concentration of circulatory inflammatory mediators was firstly investigated with two systematic reviews and a meta-analysis. We also investigated the role of reactive oxygen species in the initiation and progression of chronic inflammation, with AP being such.
Taking the information from the systematic reviews into consideration, we designed a prospective case-control intervention study, to investigate the impact of the minimum burden (1 AP). The aim of the study was: To explore the influence of apical periodontitis (AP) in inflammatory markers in blood of otherwise healthy individuals. Peripheral blood was drawn at 6 time points, 3 before and 3 after the extraction of the tooth with AP. The teeth were pulverised, DNA extraction and sequencing were performed.
The results revealed that AP has an effect on the immune fitness of the individuals. The immunologic profile of chronic apical periodontitis in one tooth and its healing profile reveals a systemic low-grade inflammation through compensatory immunosuppression. The analysis of the microbiome of the teeth with AP, revealed a difference between symptomatic and asymptomatic infections and also between primary and secondary AP. The immunologic profile of patients with asymptomatic infections was different in the concentration of some inflammatory markers, compared to symptomatic. Finally, an association between member of the microbiome of the endodontic infection and blood mediators was found. This correlation was different depending on the presence or absence of pain.