Inclusion Criteria:  Aged 18 and above Ability and willingness to give written informed consent  Exclusion Criteria:  Edentulous mouth Pregnant females Having received professional periodontal treatment (other than supragingival cleaning) within the previous 12 months Having received antibiotic medication within the previous 3 months Presence of xerostomia interfering with saliva sampling Inability or unwillingness of individual to give written informed consent