Inactivation of local root canal medicaments by dentine: an in vitro study.
OBJECTIVE
The aim of the study was to investigate the inactivation by dentine of the antibacterial activity of various commonly used local root canal medicaments.


METHODS
The medicaments tested were saturated calcium hydroxide solution, 1% sodium hypochlorite, 0.5% and 0.05% chlorhexidine acetate, and 2/4% and 0.2/0.4% iodine potassium iodide. Dentine was sterilized by autoclaving and crushed into powder with a particle size of 0.2-20 microns. Aliquots of dentine suspension were incubated with the medicaments in sealed test tubes at 37 degrees C for 24 h or 1 h before adding the bacteria. In some experiments bacteria were added simultaneously with dentine powder and the medicament. Enterococcus faecalis A197A was used as a test organism. Samples for bacterial culturing were taken from the suspensions at 5 min, 1 h and 24 h after adding the bacteria.


RESULTS
Dentine powder had an inhibitory effect on all medicaments tested. The effect was dependent on the concentration of the medicament as well as on the length of the time the medicament was preincubated with dentine powder before adding the bacteria. The effect of calcium hydroxide on E. faecalis was totally abolished by the presence of dentine powder. Similarly, 0.2/0.4% iodine potassium iodide lost its effect after preincubation for 1 h with dentine before adding the bacteria. The effect of 0.05% chlorhexidine and 1% sodium hypochlorite on E. faecalis was reduced but not totally eliminated by the presence of dentine. No inhibition could be measured when full strength solutions of chlorhexidine and iodine potassium iodide were used in killing E. faecalis.


CONCLUSIONS
The dentine powder model appears to be an efficient tool for the study of interactions between local endodontic medicaments, dentine, and microbes.
Haapasalo
H K
HK
Division of Endodontics, Dental Faculty, University of Oslo, Norway. haapasal@odont.uio.no
Sirén
E K
EK
Waltimo
T M
TM
Ørstavik
D
D
Haapasalo
M P
MP
D000891:Anti-Infective Agents, Local / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002126:Calcium Hydroxide / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002710:Chlorhexidine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D003804:Dentin / Q000737:chemistry*; D013293:Enterococcus faecalis / Q000187:drug effects; D006801:Humans; D008826:Microbial Sensitivity Tests; D011193:Potassium Iodide / Q000037:antagonists & inhibitors / Q000494:pharmacology; D012388:Root Canal Irrigants / Q000494:pharmacology*; D012973:Sodium Hypochlorite / Q000037:antagonists & inhibitors / Q000494:pharmacology
D000891:Anti-Infective Agents, Local; D012388:Root Canal Irrigants; D011193:Potassium Iodide; D012973:Sodium Hypochlorite; D002126:Calcium Hydroxide; D002710:Chlorhexidine