To address this hypothesis, a clinical study in humans with moderate to severe chronic periodontitis has been designed. This is an interventional study involving scaling and root planing and two arms: 1. treatment with PO amoxocillin/metronidazole plus chlorhexidine oral rinse; 2. no antibiotics or oral rinse. It is expected that the antibiotics plus chlorhexidine will prevent the dendritic cell response to infection (bacteremia) elicited by scaling and root planing.