A maximum of 220 subjects with a minimum of 25 years will be recruited and examined for this 1-7 visit, up to 35 days research study: Subjects will be genotyped to identify variants of the interleukin-29 (IL29) and interleukin-28B (IL28B) genes and placed in one of the 4 groups: 50 subjects with dominant allelic variants with healthy periodontium, 50 subjects with dominant allelic variants with periodontitis, 50 subjects with IL29 (rs30461) or any of IL28B (rs11083519; rs8105790; rs8099917) single nucleotide polymorphism's (SNP) variants and healthy periodontium, and 50 subjects with IL29 (rs30461) or any of IL28B (rs11083519; rs8105790; rs8099917) SNP variants and periodontitis. Visits will consist of outpatient procedures including oral examinations, oral prophylaxis or periodontal scaling and root planing, collection of gingival crevicular fluid, dental plaque, saliva, and blood samples. Analysis will include salivary DNA isolation and pyrosequencing to determine IL29 and IL28B genotype, mediator analysis of gingival crevicular fluid, dendritic cell differentiation and inflammatory mediator analysis, and whole-genome shotgun sequencing plaque analysis. Clinical outcomes will include measurements of periodontal disease progression and inflammation, such as clinical attachment level (CAL), pocket depth (PD), bleeding on probing (BOP), gingival index (GI), and plaque index (PI).