In vitro antimicrobial and cytotoxic effects of Kri 1 paste and zinc oxide-eugenol used in primary tooth pulpectomies.

The antimicrobial and cytotoxic effects of Kri 1 paste, an iodoform-based primary tooth filling material, were compared with zinc oxide-eugenol (ZOE), using in vitro techniques. Antimicrobial evaluation involved measuring inhibition zones of Streptococcus faecalis on brain heart agar. Cytotoxicity evaluation involved direct cell-medicament contact experiments of 4-hr and 24-hr duration using fresh and set medicaments, and indirect cell-medicament contact experiments of 24-hr duration using fresh and set medicaments. ZOE produced a greater zone of bacterial inhibition than Kri 1 paste. Kri 1 paste cytotoxicity remained high regardless of the amount of setting time in the 4-hr direct contact experiment, while ZOE cytotoxicity decreased with setting time. Both Kri 1 paste and ZOE had high cytotoxicity regardless of setting time in the 24-hr direct cell-medicament contact test. ZOE cytotoxicity decreased to control levels after only 1 day of setting in the indirect contact experiments, compared with greater than 7 days for Kri 1 paste. The results suggest ZOE has better antimicrobial activity than Kri 1 paste. ZOE also has lower cytotoxicity, although prolonged cell-medicament contact may result in both medicaments having similarly high cytotoxicity.