Penetrationin vitroof human and ferret dentine by three bacterial species in relation to their potential role in pulpal inflammation

摘要

Summary.Streptococcus faecaliswas able to penetrate 5 μm millipore filters and actively grew in the underlying media resulting in death of fibroblast monolayers. It was unable to penetrate 0.45 μm filters and any metabolites which it produced were non‐toxic to these cells. In spite of the reported diameter of human dentinal tubules being 1–5 μm, two bacterial species were unable to penetrate slices of human dentine. From studies using dentine powder this was shown not to be the result of binding to the dentine but from SEM studies it appeared to be due to the presence of the smear layer which occluded the openings of tubules. Removal of the smear layer allowed the rapid penetration of two motile organisms while the penetration of a non‐motile organism was accelerated when a nutrient source was present beneath the slice. Removal of the smear layerin vivomust therefore provide access for bacteria, which enter the microspace beneath restorative materials, to the dentinal tubules.Pseudomonas aeruginosawas able to digest dentine and therefore to penetrate unetched dentine slices. The presence of this organismin vivomay therefore result in severe pulpal damage. In spite of differences in the surface area of dentinal tubules between man and ferret, the pattern of penetration was similar indicating that the smear layer and its removal are much more important than the animal species used in assessing bacterially induced pulpal infl