Schematic diagram illustrating the experimental design, including rat acclimation, antibiotic treatment, PerioGard oral swabbing, preinfection oral microbial sample collection, monomicrobial infection (four to six infections) and polymicrobial infection (four infections), oral microbial sample collection (four to six times), PCR analysis, euthanasia, and gingival tissue and alveolar bone collection. For detailed information see Materials and Methods. Pg, P. gingivalis; Td, T. denticola; Tf, T. forsythia.