(PO124) Recovery of Microbial Complex Lipids From Tooth Apices is Dependent on Pulpal Status

Abstract: P. endodontalis is implicated in the destruction of periapical tissues and was reported to produce biologically active complex lipids. A previous study found an increase of the serine glycine lipid class, Lipid 654, in necrotic pulps compared to vital controls. This study sought to quantify Lipid 654 and other serine/glycine lipids recovered in teeth with necrotic pulps compared with vital pulps. Teeth from de-identified subjects were collected and separated into two groups: one with necrotic pulps and apical periodontitis and one with vital pulps without apical disease. Paired necrotic pulp tissue samples and apical tooth root samples were compared to pulp tissue and root apex samples from vital control teeth. For root apex samples, 2-3 mm of the root tip was removed, and pulp contents were removed using Hedstrom hand files. Lipids were extracted using the method of Bligh and Dyer and analyzed using negative ion mass spectrometry. Multiple Reaction Monitoring was used to quantify the lipids. The percentage abundance was calculated from integrated ion transitions. Whisker box plots revealed that the results were not normally distributed, and Kruskal–Wallis one-factor ANOVA revealed significant differences. This evaluation demonstrated that lipid extracts from necrotic root apices contain significantly higher levels of the serine/glycine lipid class, L1256. This is important because this lipid is a potent ligand for Toll-like receptor 2 in macrophages. We conclude that tooth apices from teeth with necrotic pulps and apical periodontitis have elevated levels of L1256, which may be important in apical bone loss.