Treatment protocol Patients fulfilling the eligibility criteria were asked to participate in the study and after approval to sign an informed consent. Baseline examination included full-mouth probing pocket depth , gingival recession and bleeding on probing measured at six sites per tooth. Additionally the plaque en gingival indexes were noted. The full-mouth plaque index was recorded.After baseline periodontal examination and microbial analysis, an oral hygiene instruction was given (toothbrush, interdental brush). Initial periodontal therapy consisted of a full-mouth one-stage disinfection approach . All clinical procedures were performed by the same periodontist . The patient was asked to rinse for 2 minutes with a 0.12% chlorhexidine solution without alcohol . Scaling and rootplaning were performed on 2 consecutive days using an ultrasonic scaler under 0.12% chlorhexidine irrigation and with hand instruments. All mucosal surfaces were afterwards disinfected and the tongue was brushed for 1 minute. Besides, the participants were randomized over the 2 treatment groups: control or probiotic group.The participants of the probiotic group were asked to let a probiotic tablet dissolve on their tongue 2 times a day for 3 months. The participants in the control group were asked to do the same with a placebo tablet. All patients were instructed to use the tablets after brushing their teeth in the morning and in the evening. The probiotic and placebo tablets were identical in shape, texture, taste and composition except that Streptococcus were added for the probiotic tablet. All patients were supplied with the same toothpaste . It was asked not to use any probiotic containing products during the course of the study. Neither was it allowed to use drugs with anti-inflammatory properties, chlorhexidine or other mouthrinses during the study.