The expression level of miR-34a was positively correlated with the levels of IL-1β, IL-6, and TNF-α in GCF and the periodontal clinical symptom indicators (GI, PD, AL, and PLI), confirming that miR-34a could objectively reflect the degree of the gingival crevicular inflamed condition and the severity of disease in chronic periodontitis. The gene discussed is TNF; the disease is periodontitis.