In vitro evaluation of the antimicrobial activity of mineraltrioxide aggregate supplemented with octenidine dihydrochlorideagainst Enterococcus faecalis and Candida albicans

MTA, a widely used material in dentistry, is being investigated for various improvements, particularly to enhance its antimicrobial properties. Resistant microorganisms such as E. faecalis and C. albicans can compromise the success of root canal treatments due to their ability to penetrate dentinal tubules and form biofilms. This study evaluated whether the antimicrobial activity of MTA could be enhanced by modification with octenidine dihydrochloride (OCT). OCT has emerged as an effective agent against resistant endodontic pathogens due to its broad-spectrum antimicrobial activity and low toxicity profile. The antimicrobial activity of MTA was assessed against E. faecalis (ATCC 29212) and C. albicans (ATCC 90028) using the agar diffusion method. Experimental groups included MTA + distilled water (control), MTA + its own liquid (control), MTA + 0.05% OCT, and MTA + 0.1% OCT. MTA mixtures were freshly prepared and placed into wells in agar plates, which were then left at room temperature for 2 hours to allow preliminary diffusion. Subsequently, the plates were incubated aerobically at 37 ± 1 °C, and the diameters of the inhibition zones were measured with a digital caliper at 24 and 72 hours. In tests with E. faecalis, the highest antibacterial activity at 24 hours was observed in the MTA + 0.1% OCT group (9.46 ± 1.14 mm), while the MTA + 0.05% OCT group (7.77 ± 0.55 mm) also showed significantly higher antibacterial activity compared to the control groups (p <0.05). At 72 hours, antibacterial activity decreased in all groups, and no inhibition zones were observed in the MTA + distilled water and MTA + its own liquid groups. For C. albicans, all groups exhibited antifungal activity; the highest inhibition at 24 hours was observed in the MTA + 0.1% OCT (11.80 ± 0.80 mm) and MTA + 0.05% OCT (10.74 ± 0.50 mm) groups, whereas the MTA + distilled water group showed the lowest values (p <0.05). In conclusion, within the limitations of this study, modification of MTA with OCT was found to significantly enhance its antimicrobial activity against both E. faecalis and C. albicans. Notably, MTA containing 0.1% OCT exhibited the highest inhibition among all groups and may contribute to the development of more clinically effective MTA formulations against resistant microorganisms. Keywords: Agar Diffusion Test, Candida albicans, Enterococcus faecalis, Mineral Trioxide Aggregate, Octenidine Dihydrochloride