Biofilms are composed of bacteria adhering to each other or to living or nonliving surfaces. If not removed regularly, a complex and mature biofilm develops, with up to 100 bacterial species at a single site. Supra- and subgingival oral biofilms dominated by Gram-negative anaerobic bacteria colonize and cause gingival inflammation. Subsequently, gingivitis can ensue. Take this quiz to see how much you know about biofilm control and preventing gingivitis.