After digestion by AvaII, TNF-α formed the DNA products of 70 and 63 bp for homozygous G alleles, and 63, 49 and 21 bp for homozygous A alleles.81 The detection frequency of the homozygous G allele of TNF-α was higher in the subjects with chronic periodontitis (57%) than the control group (34%) (X2: p < 0.0001, OR: 2.505, CI = 1.606 - 3.910). This evidence concerns the gene TNF and chronic periodontitis.