Most of the current knowledge of the complex microbiology of oral biofilms, which initiates and maintains periodontal lesions, has been facilitated by the introduction of molecular techniques. Several studies exalt the high sensitivity and specificity of molecular tests in the detection and quantification of periodontal pathogens. Although they have large a diffusion, the old method of bacterial culture remains nowadays the gold standard when determining the utility of a new microbial test. Moreover, cultures have the important advantage of allowing an antibiotic sensitivity test and this is much more important during the treatment of patients with aggressive periodontitis.