Table 1 Clinical criteria for patient selection

Periodontitis Resistant (PR) subjects

Age ≥ 65 years

≥ 20 natural teeth

Probing Depth at any site ≤ 5 mm

Clinical Attachment Loss at any site ≤ 2 mm

Chronic Periodontitis (CP)

≥ 4 mm Probing Depth at ≥ 30% of residual teeth

Generalized Aggressive Periodontitis (GAP)

Disease onset estimated at < 30 years based on clinical examination, past radiographs, and/or interview

≥ 6 mm Probing Pocket Depth at > 3 permanent teeth other than first molars and incisors