Evaluation of PTHrP, RANKL, and OPG Levels in Periodontal Health and Diseases

Periodontitis is a chronic inflammatory disease characterized by the destruction of tooth-supporting tissues and alveolar bone loss, primarily driven by an imbalance in bone metabolism. The regulation of bone turnover relies heavily on the balance between RANKL, which promotes osteoclast activation, and OPG, its natural inhibitor. Furthermore, PTHrP acts as a critical autocrine and paracrine regulator in periodontal tissue health and alveolar bone repair. The primary rationale of this research is to investigate the dynamic role of PTHrP in periodontal pathogenesis during both the inflammatory and tissue-destruction phases, evaluating its potential as a biological marker. Following a comprehensive clinical periodontal examination by a single calibrated clinician, specific sampling sites are isolated with cotton rolls and gently air-dried. Supragingival plaque is carefully removed prior to sampling. Gingival crevicular fluid (GCF) is then collected from these designated interproximal sites using sterile filter paper strips, which are inserted into the sulcus until mild resistance is felt and left in place for 30 seconds. Samples contaminated with blood or saliva are immediately excluded. The exact volume of the collected fluid is quantified using an electronic volume meter (Periotron 8010). All valid strips are subsequently transferred to microcentrifuge tubes and preserved at -80°C until laboratory processing. The biochemical quantification of PTHrP, RANKL, and OPG levels is performed via commercially available Enzyme-Linked Immunosorbent Assay (ELISA) kits in accordance with the manufacturer's protocols.

• Routine periodontal clinical examination and GCF collection (Other): A comprehensive clinical periodontal examination is performed by a single calibrated examiner using a periodontal probe. The examination includes the measurement of Plaque Index (PI), Gingival Index (GI), PD, and CAL. For GCF collection, the specified interproximal sites are isolated with cotton rolls, gently air-dried, and cleared of supragingival plaque. GCF samples are then collected using sterile filter paper strips inserted into the sulcus until mild resistance is felt and left in place for 30 seconds.

Primary outcomes

• GCF Level of PTHrP [Baseline (Single time point during the clinical examination)]: The concentration of PTHrP in GCF samples will be quantitatively measured using commercial ELISA kits.
• GCF Level of RANKL [Baseline (Single time point during the clinical examination)]: The concentration of RANKL in GCF samples will be quantitatively measured using commercial ELISA kits.
• GCF Level of Osteoprotegerin [Baseline (Single time point during the clinical examination)]: The concentration of OPG in GCF samples will be quantitatively measured using commercial ELISA kits.

Secondary outcomes

• Probing Depth (PD) [Baseline (Single time point during the clinical examination)]: PD will be measured using a periodontal probe at six sites per tooth (mesiobuccal, midbuccal, distobuccal, mesiopalatal/lingual, midpalatal/lingual, and distopalatal/lingual). Measurements will be rounded to the nearest millimeter.
• Clinical Attachment Level (CAL) [Baseline (Single time point during the clinical examination)]: CAL will be calculated by measuring the distance from the cementoenamel junction to the base of the probable pocket using a periodontal probe.
• Gingival Index (GI) [Baseline (Single time point during the clinical examination)]: GI will be evaluated according to the method described by Löe and Silness. Four surfaces of each tooth (buccal, lingual/palatal, mesial, and distal) will be scored to calculate the full-mouth average GI score.
• Plaque Index (PI) [Baseline (Single time point during the clinical examination)]: PI will be evaluated according to the method described by Löe and Silness. Four surfaces of each tooth will be scored to calculate the full-mouth average PI score.

Sex: All, ages: 18 Years to any, accepts healthy volunteers

Inclusion Criteria:

* Individuals aged 18 years and older.
* Presence of at least 20 natural teeth, excluding third molars.
* For the Periodontally Healthy GrouP: PD ≤ 3 mm, BOP < 10%, and no interproximal CAL or RBL.
* For the Gingivitis Group: PD ≤ 3 mm, BOP ≥ 30%, and no interproximal CAL or RBL.
* For the Periodontitis Group: Diagnosed with Stage III periodontitis (interproximal CAL ≥ 5 mm, PD ≥ 6 mm, and RBL extending to the middle third of the root or more apically).

Exclusion Criteria:

* Presence of systemic diseases that may affect periodontal tissues (e.g., cardiovascular diseases, atherosclerosis, immune system diseases, rheumatoid arthritis, obesity, cancer, and diabetes).
* Use of antibiotics within the last 3 months.
* Use of any medication that may affect periodontal tissues.
* Presence of infectious diseases such as HIV, HBV, or tuberculosis.
* Pregnancy or lactation.
* History of periodontal treatment within the last 6 months.
* Smoking