A total of approximately 128 study subjects will be enrolled into up to 7 study arms. Study drug (C16G2 Gel or Placebo) will be administered via manual brush gel application (MBGA) or tray gel application (TGA). Two C16G2 concentrations will be evaluated. Four study arms will be conducted in a double blind manner, with a treatment allocation ratio of 4:1 (C16G2:Placebo), three study arms will be conducted in an open-label manner. Before dosing, eligible subjects will undergo professional dental prophylaxis on Day 0. Clinic visits for all study arms will include Visit 1 (Screening/Days -21 to 0), and a varying number of dosing and follow-up visits.