Of the remaining 20 articles, 6 were excluded due to complete reading, where one investigated the presence of the same oral pathogens in samples of dental plaque and prostatic secretion in patients with prostatitis and periodontal disease [24], another four associated the levels with prostate specific antigen (PSA) with periodontits [31, 32, 33, 34]; and one evaluated the existence of an association between treated and untreated periodontal disease with prostate alteration [35], leaving 14 that were included in this systematic review. This evidence concerns the gene KLK3 and periodontal disorder.