Laboratory Processing, Microbiological Analysis After subgingival plaque sampling, the samples are taken immediately in the laboratory for further processing or stored in liquid nitrogen until the study is finished. After finishing the trial they will be carried to Münster. For transport they are stored in carbon dioxide snow and are stored in liquid nitrogen in the laboratory in Münster again. The pooled samples are sonicated for 10 seconds (Sonotex RK 82, Bandelin Electronic AG, Berlin, Germany) and diluted in tenfold steps. 0.1 ml of the undiluted suspension and 0.1 ml aliquots of the dilutions are spread on different culture media. In parallel supragingival plaque samples are spread on CDC agar and are stored in an aerobe atmosphere at 37 degree above zero overnight.