Vitality status of microorganisms in infected human root dentine.
OBJECTIVE
This experimental study was initiated to establish a method for characterizing the vitality status of bacteria in infected human root dentine by differentiating between viable and dead microorganisms.


METHODS
Twenty-four root segments of extracted human teeth were infected with either Streptococcus sanguinis or Enterococcus faecalis for 8 weeks. Baseline samples from root dentine (rd) were collected after 4 weeks. These were compared with samples taken at week 8 (control group: n = 12) and with samples collected at week 12 after calcium hydroxide treatment for four weeks (test group: n = 12). After marking viable and dead bacterial cells by two fluorescent dyes, the portion of viable bacteria (PVB) was determined, as well as the number of colony-forming units (CFU).


RESULTS
Viable and dead bacteria were identified in all "rd" samples. PVBrd values were lower than PVB values of the bacterial suspension in the root canal lumen. In the control group, PVBrd and CFUrd did not markedly differ at week 4 and at week 8, regardless of the strain used. In the test group, viable but non-culturable sanguinis streptococci (mean PVBrd = 27%; CFUrd = 0) were detected, despite calcium hydroxide treatment. The viability of E. faecalis was not affected by calcium hydroxide.


CONCLUSIONS
Fluorescence labelling of bacteria in human root dentine gives valuable additional information about their vitality status compared to the parameter CFU. The method may be suitable for following the fate of bacteria in dentinal tubules, for example in the presence of intracanal dressings.
Weiger
R
R
Department of Conservative Dentistry, School of Dental Medicine, University of Tübingen, Osianderstrasse 2-8, W-72076 Tübingen, Germany.
de Lucena
J
J
Decker
H E
HE
Löst
C
C
D002126:Calcium Hydroxide / Q000494:pharmacology; D015169:Colony Count, Microbial; D003804:Dentin / Q000382:microbiology*; D013293:Enterococcus faecalis / Q000187:drug effects / Q000302:isolation & purification; D005456:Fluorescent Dyes; D006801:Humans; D012107:Research Design; D012387:Root Canal Filling Materials / Q000494:pharmacology; D013298:Streptococcus sanguis / Q000187:drug effects / Q000302:isolation & purification; D014092:Tooth Root / Q000382:microbiology*
D005456:Fluorescent Dyes; D012387:Root Canal Filling Materials; D002126:Calcium Hydroxide