60 non-smoking patients with chronic moderate/severe periodontitis will be recruited from outpatient periodontal clinics at Birmingham's Dental Hospital. Subjects will be 30-60 years of age, male or female. Chronic periodontitis (CP) will be defined as the presence of 2 or more sites per quadrant with pocketing or interproximal attachment loss of > 6mm and 1/3rd radiographic bone loss.