Four weeks after starting the therapy (T1), clinical measurements and saliva samples will be harvested and serum analysis will be performed. After measurements the one-stage full-mouth disinfection will be performed as following described. Scaling and root planing of all pockets will be performed within 24 h in combination with an extensive application of chlorhexidine (0.20%) to all intra-oral niches such (periodontal pockets, tongue dorsum, tonsils) and in combination with systemic antibiotic treatment (amoxicillin cp. 1gr 2/die + 250 mg metronidazole 3/die).