Figure 1.

Study design: Visit 1=pre-screening; Visit 2=screening and chronic periodontitis diagnosis; Visit 3=baseline periodontal clinical examination, blood and gingival tissue sample collection, full-mouth scaling of all supragingival and subgingival deposits of plaque and calculus, beginning of SDD or placebo treatment; Visit 4, 5, 6, and 7=root planing and SDD or placebo treatment; Visit 8=evaluation of periodontal clinical indices, blood and gingival tissue sample collection. SRP=scaling and root planing; SDD=subantimicrobial-dose doxycycline.