Date of Graduation


Document Type


Degree Type



School of Dentistry


Not Listed

Committee Chair

John Thomas.


The purpose of this in vitro agar-diffusion study was to evaluate the effect on the antimicrobial efficacy of Hoshino's triple antibiotic paste when 0.12% chlorhexidine gluconate is substituted for the traditional propylene glycol and macrogol ointment carrier solution. Ciprofloxacin (200 mg), metronidazole (500 mg), and minocycline (100 mg), were mixed with either chlorhexidine or a 1:1 combination of propylene glycol and macrogol ointment. Seven microorganisms, including: E. coli, P. aeruginosa, S. aureus, E. faecalis, S. sanguis, F. nucleatum, and C. albicans, were incubated and plated onto triplicate blood agar plates. Two blank paper discs were positioned onto each agar plate, one saturated with chlorhexidine and the three antibiotics, and the other containing propylene glycol/macrogol ointment and the antibiotics. After appropriate incubation, a blinded, independent observer measured the zones of inhibition around each disc. Mixtures containing chlorhexidine showed significantly larger zones of inhibition in every trial (p<.004, ANOVA test). Control plates with chlorhexidine only, or propylene glycol and macrogol ointment only (no antibiotics added), further exhibited the antimicrobial properties of chlorhexidine, and the lack thereof for propylene glycol/macrogol ointment. In conclusion, substituting 0.12% chlorhexidine gluconate for propylene glycol and macrogol ointment as the carrier in Hoshino's triple antibiotic paste increased the antimicrobial efficacy of the mixture.