Cytotoxic effects and antibacterial efficacy of a 3-antibiotic combination: an in vitro study

A 3-antibiotic combination (3Mix) is widely used in endodontics for root canal disinfection, particularly in pulp revascularization procedures. However, the cytotoxicity of 3Mix has not been evaluated. The purpose of this study was to determine the cytotoxicity and antibacterial efficacy of 3Mix and each single antibiotic component of 3Mix.

For the cytotoxicity test, human dental pulp cells and apical papilla cells were exposed to either 3Mix or to each single antibiotic component of 3Mix using concentrations of 0.024, 0.097, 0.39, 1.56, 6.25, and 25.00 μg/mL for 1, 3, 5, and 7 days. Cell viability was determined using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. For the antibacterial test, 25.00 μg/mL and 0.39 μg/mL 3Mix or single antibiotic were tested on bacteria isolated from necrotic teeth by measuring bacterial recovery on blood agar.

The 0.024-μg/mL concentration of all experimental groups generated the highest dental pulp cell or apical pulp cell viability at all time periods. On day 7, 0.39 μg/mL 3Mix produced more than 90% cell viability; 25.00 μg/mL 3Mix completely eliminated isolated bacteria, whereas 0.39 μg/mL was unable to eradicate all bacteria. However, the overall bacterial reduction was significantly different compared with the control group (P < .01).

All drugs except metronidazole induced cytotoxicity on cultured cells. 3Mix generated higher cytotoxicity compared with a single drug. The cytotoxicity increased in a concentration- and time-dependent manner; 0.39 μg/mL 3Mix had less cytotoxicity and was able to significantly reduce bacteria isolated from necrotic teeth.