This observational case-control study investigates the effect of smoking on macrophage polarization in the pathogenesis of periodontitis. Adult participants who were either systemically healthy smokers or non-smokers, and who met the clinical criteria for periodontal health or periodontitis, were included. Gingival tissue samples were collected during periodontal procedures performed after completion of Phase I periodontal therapy, and the expression levels of macrophage polarization markers (iNOS and Arginase-1) were analyzed using ELISA. In addition, comprehensive clinical periodontal measurements-including probing pocket depth, clinical attachment level, bleeding on probing, Plaque Index, and Gingival Index-were recorded to evaluate the relationship between smoking status, inflammatory burden, and macrophage phenotype. The study aims to clarify how smoking modulates the balance between M1 and M2 macrophage responses in periodontal tissues.

Periodontitis is a chronic inflammatory disease in which macrophage polarization plays a key regulatory role in the host immune response. Smoking is a well-established risk factor that alters inflammatory pathways and immune cell behavior. This study was designed to examine how smoking influences macrophage polarization-specifically the balance between M1 (iNOS-mediated) and M2 (Arginase-1-mediated) phenotypes-in periodontal tissues.

Systemically healthy adult participants were recruited and categorized into four groups based on smoking status and periodontal condition: (1) healthy non-smokers, (2) periodontitis non-smokers, (3) healthy smokers, and (4) periodontitis smokers. Gingival tissue samples (approximately 2×2 mm) were collected during periodontal surgical procedures performed after completion of Phase I periodontal therapy, immediately stored at -80 °C, and processed for biochemical analysis. Comprehensive clinical periodontal measurements-including probing pocket depth (PPD), clinical attachment level (CAL), bleeding on probing (BOP), Plaque Index (PI), and Gingival Index (GI)-were recorded on the same day to evaluate periodontal status and inflammatory burden. ELISA was used to quantify iNOS and Arginase-1 levels in gingival tissues.

The primary objective of this study is to determine whether smoking shifts the macrophage phenotype toward a more pro-inflammatory M1 profile or suppresses M2-associated regulatory pathways in the context of periodontitis. The findings are expected to contribute to a better understanding of smoking-related alterations in periodontal immune mechanisms.

Inclusion Criteria:

• The study population consisted of volunteer participants aged 18-65 years who were referred to the Department of Periodontology at Süleyman Demirel University Faculty of Dentistry for periodontal treatment and who met the inclusion criteria without violating any exclusion criteria.

Exclusion Criteria:

• Individuals who did not consent to participate in the study
• History of any periodontal treatment within the past 6 months
• Use of systemic antibiotics within the past 3 months
• Pregnancy or lactation
• Psychological or physical conditions that may interfere with cooperation during clinical examination
• History of substance or alcohol abuse
• Presence of severe malocclusion or ongoing orthodontic treatment
• Acute dental pain due to caries, abscess, or other odontogenic infections
• Presence of systemic diseases with oral manifestations or any systemic condition known to affect periodontal tissues
• History of malignancy
• Use of medications that can influence periodontal parameters (e.g., anti-inflammatory drugs) within the past 3 months
• Participation in another scientific or clinical research study within the past 3 months

The study population consisted of systemically healthy volunteer adults aged 18-65 years who presented to the Periodontology Clinic of Süleyman Demirel University Faculty of Dentistry with a need for periodontal treatment. Eligible participants were assigned to one of four groups based on smoking status and periodontal condition: healthy non-smokers, periodontitis non-smokers, healthy smokers, and periodontitis smokers. All participants were evaluated according to the study's predefined inclusion and exclusion criteria before enrollment.

Individual participant data will not be shared because this study is a single-center thesis research project, and data sharing is not permitted under institutional and ethical regulations.