In relation to biomarker levels in healthy and periodontitis sites according to severity (Table 2), MMP-8 had the highest levels (means) in severe periodontitis sites (464.20 ng/mL), followed by mild periodontitis sites (270.82 ng/mL), and healthy sites (60.49 ng/mL), with statistically-significant differences among all groups observed in the adjusted multilevel linear regression model (p ≤ 0.01). The gene discussed is MMP8; the disease is periodontitis.