The aim of this study is to evaluate and compare the levels of bone resorption (RANKL, OPG) and oxidative stress (Nitrotyrosine, NQO1) markers, along with pro-inflammatory cytokines (IL-1β), in the saliva and peri-implant sulcular fluid (PISF) of patients with peri-implantitis, periodontitis, and healthy individuals. The study seeks to determine the diagnostic value of these biomarkers in the early detection and progression of peri-implant diseases.

Patients applying to the University of Health Sciences, Gulhane Faculty of Dentistry, Department of Periodontology, will be screened according to the inclusion and exclusion criteria. Following clinical and radiographic examinations, participants will be categorized into four groups (n=20 per group): Periodontitis, Peri-implantitis, Periodontal Health, and Peri-implant Health. All clinical parameters, including Plaque Index (PI), Gingival Index (GI), Bleeding on Probing (BOP), Probing Depth (PD), and Clinical Attachment Loss (CAL), will be recorded at six sites per tooth/implant using a Williams periodontal probe.

The biological sample collection protocol will be conducted as follows:

Saliva Collection: To minimize circadian rhythm variations, unstimulated whole saliva samples (3 ml) will be collected between 9:00 AM and 10:00 AM. Patients will be instructed to refrain from eating, drinking, or oral hygiene procedures for at least one hour prior to collection. Samples will be centrifuged at 1,000g for 10 minutes to remove cellular debris, and the supernatant will be stored at -80°C until laboratory analysis.

Peri-implant Sulcular Fluid (PISF) and Gingival Crevicular Fluid (GCF) Collection: Samples will be obtained from the site with the deepest probing depth in each participant. The area will be isolated with cotton rolls and gently dried with an air syringe to prevent salivary contamination. Periopaper strips will be inserted into the sulcus/pocket for 30 seconds. Strips contaminated with blood or visible saliva will be discarded.

Laboratory Analysis: The concentrations of Interleukin-1 beta (IL-1β), Nitrotyrosine, Receptor Activator of Nuclear Factor Kappa-B Ligand (RANKL), Osteoprotegerin (OPG), and NAD(P)H: Quinone Oxidoreductase 1 (NQO1) will be quantified in both saliva and PISF/GCF samples using commercially available Enzyme-Linked Immunosorbent Assay (ELISA) kits according to the manufacturer's instructions.

Inclusion Criteria:

Systemically healthy volunteers aged 18-65. For Peri-implantitis group: Implants in function for ≥1 year, radiographic bone loss ≥ 2 mm, probing depth (PD) ≥ 5 mm, and presence of bleeding on probing (BOP) or suppuration.

For Periodontitis group: At least one tooth with PD ≥ 4 mm, presence of BOP, and radiographic bone loss.For Healthy groups: PD ≤ 3 mm, no clinical inflammation (BOP-), and no radiographic bone loss.

(According to the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases) -

Exclusion Criteria:Presence of systemic diseases (e.g., diabetes, rheumatoid arthritis, osteoporosis).

Use of antibiotics, anti-inflammatory, or immunosuppressive drugs within the last 3 months.

Pregnancy or breastfeeding.

Smoking (current smokers).

History of periodontal or peri-implant surgical treatment within the last 6 months.

Implant failure (mobility).

Signs of acute infection (fever, systemic symptoms).

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Patients who apply to the University of Health Sciences, Gulhane Faculty of Dentistry, Department of Periodontology, and meet the specific clinical and radiographic criteria for peri-implantitis, periodontitis, or health.

The individual participant data will not be shared to protect participant privacy.