Systems and methods for treating gingival tissue or oral biofilm includes applying to the gingival tissue (sulcus or periodontal pocket) a biofilm penetrating antimicrobial agent; removing the imbedded anaerobic bacteria from the gingival tissue following at least one applying of the antimicrobial agent to the gingival tissue; administering colloidal hydrogen peroxide gel to the gingival tissue following the removing of imbedded anaerobic bacteria; and cleaning the gingival tissue with a cleaning agent directly following the administering of the colloidal hydrogen peroxide gel for modifying the environment from anaerobic (diseased) to aerobic (healthy).