For quantitative enumeration the undiluted and diluted suspensions are spread on non-selective blood agar (CDC agar) plates containing 5% defibrinated sheep blood supplemented with 5mg/l hemin (Merck, Darmstadt, Germany), 1 mg/l vitamin K1, and 10 mg/l N-acetylmuramine acid (NAM). NAM is supplemented for cultivation of T. forsythensis. The plates are incubated in an atmosphere containing N2 (85%), H2 (10%), and CO2 (5%) for 7 days. Total cultivable counts are assessed for each of the plaque samples. The evaluation of pooled plaque samples on CDC agar and the total cultivable counts are reported quantitatively as colony forming units (CFU/ml). In further investigation the present of specific periodontal pathogens will be evaluated.