ANTIBACTERIAL ACTIVITY OF MDPB POLYMER INCORPORATED IN DENTAL RESIN

Objectives: Previously, we have reported that dental composite incorpo rating the new monomer methacryloyloxydodecylpyridinium bromide (MDPB) showed no release of antibacterial components after being cured but s till exhibited antibacterial activity against Streptococcus mutans on its surface. In this study, in order to elucidate the mechanism of the antibacterial effect of immobilized MDPB, the bactericidal activity o f MDPB polymer in water-soluble and -insoluble form was investigated, and the effect of MDPB polymer on bacterial attachment was estimated. Methods: Solutions of homo-polymer of MDPB and co-polymer of MDPB with acrylamide were prepared and the viability of seven major oral strept ococci was determined after incubation with each polymer solution. For the estimation of bactericidal activity of insolubilized MDPB polymer , bacteria were kept in contact with cured unfilled Bis-GMA-based resi n discs with or without MDPB, and the recovery of viable cells was mea sured. Attachment of streptococci to cured resin discs with or without MDPB was also compared using radiolabelled bacteria. Results: Water-s oluble homo-polymer of MDPB and co-polymer with acrylamide showed bact ericidal activity against oral streptococci. However, cured resin inco rporating MDPB, which is in water-insoluble form, had little bacterici dal activity. Attachment of streptococci, including species which are early colonizers in dental plaque formation, to the cured resin contai ning MDPB was significantly less than to the control without MDPB. Con clusions: These results indicate that the bactericidal activity of MDP B polymer is reduced after immobilization, but MDPB on the surface of a resin-based material still shows a bacteriostatic effect and antiadh esion property against oral streptococci.