Periodontal ligament-associated protein-1 (PLAP-1) and sclerostin play an important role in the suppression of bone formation. Tumor necrosis factor-alpha (TNF-α) is an important proinflammatory cytokine involved in periodontal bone loss. This study aims to investigate gingival crevicular fluid (GCF) PLAP-1, sclerostin and TNF-α levels in individuals with periodontal disease. Totally 71 systemically healthy and non-smoker individuals consisting of stage 3 grade C periodontitis (n=23), gingivitis (n=24) and periodontally healthy (n=24) were enrolled. Periodontal status was evaluated by measuring the full-mouth clinical periodontal parameters. GCF PLAP-1, sclerostin and TNF-α total amounts were measured by ELISA. Data were analyzed using non-parametric statistical tests.

According to the clinical and radiographic criteria outlined in the 2017 International Workshop on the Classification of Periodontal and Peri-implant Diseases and Conditions participants were categorized into three distinct groups based upon their periodontal status: 1) 23 patients with stage 3 grade C (S3GC) periodontitis; 2) 24 patients with gingivitis; and 3) 24 periodontally healthy individuals.

Periodontal clinical parameters including probing depth (PD), clinical attachment loss (CAL), the dichotomous recording (present/absent) of bleeding on probing (BOP), gingival index (GI) and plaque index (PI) were recorded at six sites (mesio-buccal, mid-buccal, disto-buccal, mesio-lingual, mid-lingual, and disto-lingual) per tooth, except the third molars.

GCF sampling was performed on the day following periodontal examination. GCF was sampled from the buccal aspects of non-adjacent proximal sites in two single-rooted teeth. Samples were obtained from two deepest pockets in periodontitis group and were taken from the sites with visible signs of inflammation in gingivitis group. GCF samples were collected from sites with no clinical inflammation in the healthy controls. Standardized paper strips were used for GCF sampling. The amount of collected GCF was measured by a precalibrated electronic device.

PLAP-1, sclerostin and TNF-α levels in GCF samples were measured by the enzyme-linked immunosorbent assay (ELISA) via commercial kits, in line with the manufacturer's guidelines. GCF results for three analytes were expressed as total amounts (ng).

All data analyses were carried out using a statistical package. Normality of the clinical and biochemical data was first checked by Shapiro Wilk's normality test. Comparisons of clinical parameters and GCF PLAP-1, sclerostin and TNF-α levels among the study groups were performed using Kruskal-Wallis test, followed by Dunn-Bonferroni post hoc test. The possible correlations of GCF biomarker levels with clinical periodontal parameters and also with each other were determined by Spearman rank correlation analysis.

Inclusion Criteria:

• no history of smoking (determined by self-reporting)
• had a minimum of 18 natural remaining teeth (excluding third molars).

Exclusion Criteria:

• suffered from diabetes mellitus, rheumatoid arthritis, cardiovascular and respiratory system diseases, hepatic and renal failure, metabolic bone diseases, endocrine disorders, immunologic and mucocutaneous diseases
• used immunosuppressive agents, antibiotics, anti-inflammatory and anti-resorptive drugs, topical antiseptic solutions, calcium channel blockers, beta-blockers, anticoagulants and hormonal contraceptives within the past 3 months
• pregnant or lactating
• received any periodontal intervention in the past year
• used removable partial dentures or orthodontic appliances

A total of 71 systemically healthy and never-smoker individuals (34 males and 37 females and; aged 27 to 46 years) were consecutively included for this cross-sectional study.