A review of the literature revealed that while there are studies investigating the relationship between vitamin D and periodontal disease, there are no studies investigating the anti-inflammatory effect of vitamin D on periodontal disease. Investigators hypothesized that the increased incidence of periodontal disease in individuals with vitamin D deficiency might be due not only to pro-inflammatory effects but also to impaired bone metabolism and a decrease in the anti- inflammatory mechanism. Investigators aimed to determine this by comparing serum and DOS levels of 1,25-dihydroxyvitamin D (1,25(OH)2D), 25-hydroxyvitamin D (25(OH)D3), Receptor activator nuclear kappa B ligand (RANKL), osteoprotegerin (OPG), Tumor Necrosis Factor Related Apoptosis induced Ligand (TRAIL), Developmental endothelial locus (Del)-1, Lipoxin, Resolvin, interleukin (IL)-10, and transforming growth factor-β (TGF-β).

The study will include 120 individuals who are systemically healthy based on clinical and radiographic examinations and diagnosed with Stage I-II periodontitis, Stage III-IV periodontitis, chronic gingivitis, and periodontally healthy. Periodontal clinical parameters (Probing pocket depth (PPD), Clinical attachment level (CAL), Bleeding on probing (BOP), Plaque index (PI), Gingival index (GI)) will be recorded three times: before treatment, and 6 and 12 weeks after treatment. Gingival crevicular fluid (GCF) and serum samples will be collected from participants at baseline and 12 weeks later for biochemical analysis.

Inclusion Criteria:

• Study groups will be formed according to the 2017 Periodontal Disease Classification. Accordingly:
• Periodontally healthy; absence of bleeding on probing, erythema, edema, patient symptoms, attachment, and bone loss
• Gingivitis; patients with an average gingival index ≥0.5 according to Löe and Silness
• Stage I-II periodontitis; patients with CAL 1-2 or 3-4 mm and a maximum PPD ≤5 mm, showing radiographic horizontal bone loss up to the coronal third of the root (15%-33%), but without tooth loss due to periodontitis
• Stage III-IV periodontitis; Stage 3 and 4 patients with ≥15 teeth in their mouth, with CAL ≥5 and PPD ≥6 in at least 6 areas, and radiographic bone loss extending to the middle or apical third of the root.

Exclusion Criteria:

• Individuals who have undergone periodontal treatment in the last 6 months, have systemic diseases (such as diabetes, parathyroid and thyroid-related endocrine diseases) that may affect periodontal status, patients with chronic liver disease, hypoparathyroidism and renal failure, those who have been using medications that may affect periodontal response (aspirin, non-steroidal anti-inflammatory drugs or steroids) for a long time, those who are using additional vitamin D or calcium supplements in the pre-study phase, those who are pregnant or breastfeeding, and those with hypercalcemia and malabsorption syndrome will not be included in the study.