To verify the clinical inflammatory status of the patients with periodontitis and resolution by periodontal therapy, we performed PCA using six variables: erythrocyte sedimentation rate (ESR) and CRP, which are indicators of inflammation; probing pocket depth (PPD), clinical attachment level (CAL), plaque index (PI), and gingival index (GI), which are indicators of the severity of periodontitis. The gene discussed is CRP; the disease is periodontitis.