Modeling bacterial damage to pulpal cells in vitro

There is increasing evidence that access to patent dentinal tubules by bacteria and their products rather than trauma from restorative materials is responsible for subsequent pulpitides. The purpose of this study was to compare the relative cytotoxicity of centrifugal fractions of two bacteria, Fusobacterium nucleatum and Treponema denticola, on L929 cells in monolayer cultures and in the "in vitro pulp chamber." Neutrophilic chemotaxis assays and Limmulus assays were performed to verify biological activity of the various fractions of these bacteria. It was found that T. denticola inhibits new protein synthesis in cultured cells to a much greater extent than F. nucleatum, but that only F. nucleatum fractions are chemoattractive for human neutrophils in the absence of serum. While the chemical nature and molecular weights of the "toxic" materials were not determined, it appeared that eukaryotic protein synthesis inhibition caused by the T. denticola pellet fraction in the in vitro pulp chamber was at least 1000 times less than that caused by the same concentrations in monolayer cultures.