Zinc oxide-eugenol (ZOE)-containing restorative materials are, in addition to a regular intermediate restorative material, used during stepwise excavation of deep caries and as a coronal seal to prevent access of bacteria to the root canal during and after endodontic treatment. This highlights the importance of the antibacterial properties of the material, to kill remaining bacteria during excavation and bacteria that may penetrate the coronal restoration of an endodontically treated tooth. Chitosan has been reported to have an antimicrobial effect against bacteria. The aim of the study was to increase the antibacterial efficacy of a ZOE-containing restorative material.



Chitosan and chitosan-oligosaccharide (20 wt%) was mixed with ZOE powder (IRM, Dentsply) before eugenol was added. The material was allowed to set overnight. Streptococcus mutans, Enterococcus faecalis and Staphylococcus epidermidis was used for biofilm experiments and direct contact test (DCT). S. epidermidis was used for live/dead staining after DCT and examined using a fluorescence microscope. The biofilm inhibitory effect was quantified using resazurin (10µg/ml) on 6 hours biofilm. DCT was performed on the material coated in microtiter plates. Bacteria (ca. 106) was left in contact with the material for 1 hour at 37°C before colonization on BHI agar. CFU was counted the following day.



Chitosan and chitosan-oligosaccharide increased the antibacterial effect of the ZOE-containing material against S. mutans, S epidermidis and E. faecalis after 1 hour contact. DCT and live/dead staining of S. epidermidis showed more dead cells on the ZOE material containing chitosan and chitosan-oligosaccharide compared to control (ZOE). In addition, chitosan and chitosan-oligosaccharide incorporated in ZOE-material reduced early biofilm formation of the three bacterial species investigated.



Chitosan and chitosan-oligosaccharide incorporated into a ZOE-containing restorative material increases the antibacterial and anti-biofilm effect. Future studies will investigate the impact on the sealing ability of the material and mechanical effects.



Inger Sofie Dragland, Ida S. R. Stenhagen, Hilde B. Molvig Kopperud, Håkon Valen