Antimicrobial additives were incorporated into the monomer system used in the restorative process of dental fillings that have the potential to reduce secondary cavities. Untreated resins lacked an inhibitory effect towards the bacteria, Streptococcus mutans. Ampicillin was added as a positive control, with methacrylic acid and copper(II)-methacrylate being the compounds of interest. After an initial antimicrobial effect, it was observed that the resins displayed a gradual decline with soak time.