This study evaluates the effect of non-surgical periodontal therapy on salivary biomarkers (Dkk-1, Sclerostin, and PLAP-1) and clinical periodontal parameters in patients with periodontitis. Periodontitis is a chronic inflammatory disease that destroys tooth-supporting tissues. Smoking is a significant risk factor that worsens periodontal destruction and reduces the effectiveness of standard therapies.

• The trial is a non-randomized comparative clinical study.
• It includes 44 adult patients diagnosed with Stage II and III periodontitis.
• The participants are divided into two equal groups: 22 current smokers and 22 non-smokers.
• Participants will undergo a baseline examination, followed by standardized non-surgical periodontal therapy consisting of scaling and root planing.
• A follow-up visit will be conducted six weeks post-therapy to repeat clinical measurements and saliva collection.
• The primary objective is to evaluate changes in salivary biomarker levels and clinical parameters (Plaque Index, Gingival Index, bleeding on probing, Probing Pocket Depth, Clinical Attachment Level) after treatment.

Smoking is known to adversely affect the periodontium by altering cytokine production, impairing neutrophil function, and causing vasoconstriction that masks clinical inflammation. Because conventional diagnostic methods primarily measure past tissue destruction, there is growing interest in utilizing salivary biomarkers for real-time monitoring of disease activity. Specifically, Dickkopf-1 (Dkk-1) and Sclerostin (SOST) are elevated in periodontitis and actively suppress bone formation by antagonizing the Wnt/β-catenin pathway. Conversely, Periodontal Ligament-Associated Protein-1 (PLAP-1) plays a protective role in maintaining the periodontal ligament, and its presence in saliva may indicate active degradation. The collective behavior of these biomarkers in response to therapy among smokers is not fully understood.

This non-randomized comparative clinical trial aims to investigate the impact of smoking on these salivary biomarkers before and after non-surgical periodontal therapy. A total of 44 systemically healthy adult participants with Stage II and III periodontitis will be enrolled. The participants will be divided into two groups of 22: current smokers and non-smokers (defined as having never smoked or quit >5 years ago).

Study Procedures:

• Baseline Visit: Participants will provide written informed consent, followed by the collection of unstimulated whole saliva via passive drooling. A full-mouth clinical examination will then be conducted using a UNC-15 periodontal probe. Clinical measurements include Plaque Index (PLI), Gingival Index (GI), Gingival Bleeding Index (GBI), Probing Pocket Depth (PPD), and Clinical Attachment Level (CAL).
• Treatment Phase: Patients will receive standardized non-surgical periodontal therapy. This involves scaling at the first visit, followed by root planing after one week.
• Follow-up Visit: Six weeks after completing the therapy, participants will return for a second saliva collection and a repeat of all clinical periodontal examinations.

Laboratory and Statistical Analysis:

• Saliva samples will be kept in an ice box, centrifuged at 3000 rpm for 10 minutes, and the supernatant stored at -40 °C.
• Salivary levels of Dkk-1, SOST, and PLAP-1 will be quantified using specific human ELISA kits.
• Statistical analysis will assess intra-group and inter-group changes using SPSS, with a statistical significance level set at p ≤ 0.05.

Inclusion Criteria:

• Systemically healthy.
• Diagnosed with Stage II and III periodontitis.
• Presence of ≥ 20 teeth (excluding third molars).
• Current smoker OR non-smoker

Exclusion Criteria:

• Presence of systemic diseases affecting the periodontium.
• Use of medications affecting inflammation.
• Received periodontal therapy in the past 6 months.
• Received antibiotic therapy in the last 3 months.
• Alcohol use.

De-identified individual participant data will be made available upon reasonable request to the Principal Investigator.