Participants eligible for inclusion are those who have reported a lifetime history of never smoking and exhibit periodontal health.

Tobacco Use: Participants must have a documented history of smoking more than 10 cigarettes per day.

Periodontal Health: Participants must exhibit clinically verified periodontal health, characterized by the absence of clinical attachment loss, probing depths within normal ranges, and no radiographic evidence of alveolar bone loss.

Non-smokers: Only participants who have reported never smoking will be considered.

Clinical Attachment Loss: Participants must exhibit a clinical attachment loss (CAL) of ≥3 mm in more than 30% of sites.

Probing Depth: A probing depth (PD) of ≥5 mm must be present in at least six teeth.

Radiographic Bone Loss: Participants must show radiographic evidence of bone loss extending to or beyond the middle third of the root in the coronal third.

Smoking History: Participants must have reported smoking more than 10 cigarettes per day for a period exceeding 5 years.

Clinical Attachment Loss (CAL): Participants must exhibit a clinical attachment loss of ≥3 mm in more than 30% of examined sites.

Probing Depth (PD): A probing depth of ≥5 mm must be present in at least six teeth.

Radiographic Bone Loss: Participants must demonstrate radiographic evidence of bone loss extending to or beyond the middle third of the root in the coronal third.

Saliva samples will be collected from all participants, and comprehensive clinical parameters will be meticulously documented. The Plaque Index (PI) and Gingival Index (GI) will be measured at four sites per tooth. Full-mouth probing depth (PD) and clinical attachment level (CAL) will be recorded in detail for each tooth at six sites. The percentage of bleeding areas will be assessed within 20 seconds post-probing using a binary scoring system to indicate presence or absence. All clinical parameters will be recorded by a calibrated periodontologist utilizing manual probing techniques.

Following collection, saliva samples will be stored at -80°C until subsequent analysis. Concentrations of IL-39, IL-41, IL-1β, and TNF-α in the saliva samples will be quantified using specific enzyme-linked immunosorbent assay (ELISA) kits.

The measurements will be performed using a Williams periodontal probe (Hu-Friedy, Chicago, IL, USA) and will include plaque index (PI) at six sites per tooth (mesio-buccal, buccal, disto-buccal, mesio-lingual, lingual and disto-lingual) on each tooth.

Plaque Index (PI) Unit: Numerical score

Levels of IL-39, IL-41, IL-1β, and TNF-α saliva samples (ng/L) Unit: Picograms per milliliter (pg/mL)

IL-39, IL-41, IL-1β, and TNF-α levels will be assayed with commercially available kits using the enzyme-linked immunosorbent assay (ELISA) method.

The measurements will be performed using a Williams periodontal probe (Hu-Friedy, Chicago, IL, USA) and will include percentage bleeding on probing (BOP) at six sites per tooth (mesio-buccal, buccal, disto-buccal, mesio-lingual, lingual and disto-lingual) on each tooth.

Percentage Bleeding on Probing (BOP) Unit: Percentage (%)

The measurements will be performed using a Williams periodontal probe (Hu-Friedy, Chicago, IL, USA) and will include clinical attachment level (CAL) at six sites per tooth (mesio-buccal, buccal, disto-buccal, mesio-lingual, lingual and disto-lingual) on each tooth.

Clinical Attachment Level (CAL) Unit: Millimeters (mm)

The measurements will be performed using a Williams periodontal probe (Hu-Friedy, Chicago, IL, USA) and will include gingival index (GI) at six sites per tooth (mesio-buccal, buccal, disto-buccal, mesio-lingual, lingual and disto-lingual) on each tooth.

Gingival Index (GI) Unit: Numerical score