Spin-inoculation increases P. gingivalis W83 invasion of EC and SMC at M.O.I. of 100. For spin inoculation, after the addition of the bacteria, the plate was centrifuged at 1000 × g for 10 minutes at room temperature. Three hours post invasion, the intracellular P. gingivalis was enumerated by immunofluorescent staining (2A) and recovered on BAP (2B). For immunofluorescent staining, five fields were viewed and the percentage of P. gingivalis-containing cells was calculated. Means and standard deviations are derived from five different fields. For CFU on BAP, the means and standard deviations were derived from four separate experiments.