Current concepts of the causes of periodontitis implicate a bacterial infection as the primary cause of the disease. Several bacterial species residing in a biofilm on tooth surfaces are closely associated with periodontitis. Chronic periodontitis (CP) is initiated and sustained by bacterial plaque, but host defense mechanisms play an integral role in its pathogenesis.

Gene expression profiling is a powerful means of generating comprehensive genome-level data sets on diseases such as cancer, asthma, rheumatoid disorders and periodontitis, and provides significant insight information for these diseases. Gene expression profiling may provide an evidence for involving genes in the pathogenesis of CP and generate further information other than clinical signs and symptoms of CP.

The aim of this study was to identify gene-expression patterns of patients with chronic periodontitis by whole-transcriptome gene-expression analyses.

Inclusion Criteria:

1. CP patients had at least 20 teeth exhibiting >30% of measured sites with >5mm clinical attachment loss.
2. Had bleeding on probing (BOP) at >50% of the proximal sites.

Exclusion Criteria:

1. Had any known systemic diseases that can influence the periodontal status, oral diseases other than chronic periodontitis and ongoing orthodontic therapy.
2. History of hepatitis, HIV infection, or diabetes; requirement for antibiotic prophylaxis, pregnancy or lactation; and long-term use of anti-inflammatory drugs.
3. Should be free of systemic diseases
4. Individuals had to be older than 18 years of age.

The patientswere recruited from those patients seeking dental treatment in Kocaeli University, Faculty of Dentistry Periodontology Clinics.