In vitro evaluation of the antibacterial activity of cured dentin/enamel adhesive incorporating the antimicrobial agent MDPB

The aim of this study was to investigate in vitro the antibacterial effect of a dentin/enamel adhesive containing MDPB (Clearfil Protect Bond) after curing and to compare it with an adhesive not containing MDPB (Clearfil SE Bond). The antibacterial effect of the cured adhesives was tested on Enterococcus faecalis by the evaluation of growth inhibition in a 48-h microplate direct contact test (DCT). The presence of antibacterial activity due to soluble components was also investigated by an agar diffusion test (ADT) performed with the adhesives cured on the surface of dentin disks. In the DCT, both the tested materials showed complete inhibition of bacterial growth until the 7-h reading, regardless of whether direct contact with the bacterial inoculum was continued or limited to 1 h. Stationary growth phase turbidity levels were observed at 24 or 48-h incubation. The ADT produced no inhibition areas around the dentin disks. Both adhesives tested in vitro under conditions simulating those encountered in the restorative treatment of dental caries were equally able to delay bacterial growth demonstrating a similar bacteriostatic effect. As suggested by both the DCT and the ADT, the antibacterial effect of the two adhesives depends on direct contact and does not seem to be related to the diffusion of soluble components.