Bacterial invasion into radicular dentine—an in vitro study
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We wanted to investigate differences in invasiveness into radicular dentinal tubules by monocultured and co-cultured bacteria frequently found in infected root canals.
Fifty-one human roots were incubated for 8 weeks with monocultured Streptococcus gordonii ATCC 10558, Streptococcus sanguinis ATCC 10556, and with five capnophiles/anaerobes as well as with capnophiles/anaerobes co-cultured with a streptococcal species. Thereafter, bacterial samples were cultured from the inner, middle, and outer third of the root dentine of longitudinally broken teeth (n = 5). In addition, scanning electron microscopy (SEM) images were obtained.
Single gram-positive species were able to penetrate into the middle and outer third of the root dentine. Fusobacterium nucleatum ATCC 25586 was not found in any of the dentine specimens. Prevotella intermedia ATCC 25611 and Porphyromonas gingivalis ATCC 33277 were found in the inner and middle third.
The bacterial load of streptococci was higher in all thirds in co-cultures compared to single infections. In co-cultures with streptococci, Actinomyces oris ATCC 43146 was found in the outer third in 9/10 samples, whereas P. intermedia ATCC 25611 was not detectable inside dentine. Co-culture with S. sanguinis ATCC 10556 enabled F. nucleatum ATCC 25586 to invade dentine; SEM images showed that F. nucleatum ATCC 25586 had a swollen shape.
Invasiveness of bacteria into dentinal tubules is species-specific and may change depending on culturing as a single species or co-culturing with other bacteria.
Oral streptococci may promote or inhibit invasion of capnophiles/anaerobes into radicular dentine.
KeywordsBacterial invasion Root dentine Scanning electron microscopy Co-culture Monoculture Dentinal tubules
The authors are grateful to Stéphanie Larti, Anna Magdon, and Marianne Weibel (University of Bern, Department of Periodontology, Laboratory of Oral Microbiology) for their technical assistance.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
The work was supported by the participating institutions.
This article does not contain any studies with human participants or animals performed by any of the authors.
For this type of study, formal consent is not required.