Microbiological and immunological investigation of periapical pathosis

Infection of the root canal system of a tooth results in pathological changes consistent with both non-specific inflammation and specific immunological reactions. In this investigation, fifty strains of microorganisms were isolated from the apical 5-6 mm of ten teeth with cariously exposed pulp chambers. A mouse model was developed to macroscopically evaluate the pathogenic effects of oral microorganisms associated with endodontic disease. Explant cultures of periapical lesions were cultured with tritiated amino acids in enriched RPMI-1640 medium. Staph Protein A affinity columns were used to purify the labeled IgG in the supernatant fluids. The in vitro biosynthesis of IgG was demonstrated by detecting a significant difference in scintillation counts between the purified Staph Protein A eluent (IgG) and cocktail blanks. A dot enzyme-linked immunosorbent assay (Dot-ELISA) was used to determine the reactivity of IgG in the supernatant fluids of explant cultures of periapical lesions with a panel of ten microorganisms implicated in infections of endodontic origin. When 90 supernatant fluids were tested, black-pigmented Bacteroides/Porphyromonas (BPBP) were the microoganisms most often reacting by a Dot-ELISA (B. intermedius-84%, P. endodontalis-58%, and P. gingivalis-50%). A lack of cross reactivity with other BPBP was demonstrated by adsorbing each of four supernatant fluids with each of four BPBP and then testing for reactivity by a Dot-ELISA. A radial immunodiffusion assay was used to detect and quantitate the amount of IgG, IgA, and IgM in the supernatant fluids of explant cultures of periapical lesions. IgG was the predominant immunoglobulin followed by IgA but, IgM was not detected. A radioimmunosorbent test was used to demonstrate IgE in supernatant fluids from explant cultures of periapical lesions. An ELISA was used to determine the difference in reactivity of serum IgG to a panel of ten oral anaerobic microorganisms implicated in infections of endodontic origin. B. intermedius was associated with both endodontic and periodontal disease while P. gingivalis was associated with only periodontal disease. The results suggest that BPBP are important in polymicrobial infections of endodontic origin.