AbstractBackgroundThe aim of this study was to investigate an in vitro dynamic bioreactor model by evaluating the antimicrobial effect of clinically relevant amoxicillin doses on polymicrobial microcosm biofilms derived from subgingival plaque.MethodsBiofilms from pooled subgingival plaque were grown for 108 hours in control and experimental dynamic biofilm reactors. Amoxicillin was subsequently infused into the experimental reactor to simulate the pharmacokinetic profile of a standard 500 mg thrice‐daily dosing regimen over 5 days and biofilms were assessed by live/dead staining, scanning electron microscopy, and quantitative polymerase chain reaction.ResultsFollowing establishment of the oral microcosm biofilms, confocal imaging analysis showed a significant increase in dead bacteria at 8 hours (p = 0.0095), 48 hours (p = 0.0070), 96 hours (p = 0.0140), and 120 hours (p < 0.0001) in the amoxicillin‐treated biofilms compared to the control biofilms. Nevertheless, viable bacteria remained in the center of the biofilm at all timepoints. Significant reductions/elimination in Campylobacter rectus, Tannerella forsythia, Aggregatibacter actinomycetemcomitans, and Peptostreptococcus anaerobius was observed among the amoxicillin‐treated biofilms at the 96 and 120 hour timepoints.ConclusionA novel in vitro dynamic model of oral microcosm biofilms was effective in modeling the antimicrobial effect of a pharmacokinetically simulated clinically relevant dose of amoxicillin.