The aim of the study is to evaluate the effect of obesity on periodontally healthy or diseased tissues.Normal weight and obese subjects were analyzed in 6 groups. Clinical periodontal status was determined through plaque index, gingival index, bleeding on probing, pocket probing depth, clinical attacment level and radiographs.

Oxidative stress is known to contribute to various diseases by affecting cellular functions through the oxidation of proteins, lipids and DNA. Oxidative stress can be assessed by measuring the products of oxidative damage found in proteins, lipids and DNA or reductions in total antioxidant capacity Malondialdehyde, protein carbonyl and total antioxidant capacity levels are biomarkers of oxidative stress in gingival crevicular fluid.

This cross-sectional study was conducted with 93 subjects (45 normal-weight, and 48 class I obese) recruited from the Periodontology Department at the Ondokuz Mayıs University Faculty of Dentistry; Endocrinology and Metabolic Diseases Department at the Ondokuz Mayıs University Faculty of Medicine in Turkey, between September 2012 and March 2014.

The study protocol was approved by the Local Ethics Committee, and written informed consent was obtained from all study participants in accordance with the Helsinki Declaration (revised in 2000).

Oxidative stress occurs when the balance between reactive oxygen species and antioxidants become unbalanced. OS can be determined by evaluation of oxidative damage products in proteins, lipids and DNA or the reduction of total antioxidant capacity.

Malondialdehyde level is the biomarker of oxidative stress in lipids. Protein carbonyl level is the biomarker of oxidative stress in proteins.Total antioxidant capacity level is another biomarker of oxidative stress. Malondialdehyde, protein carbonyl and total antioxidant levels in crevicular fluid were examined by ELISA method.

Obesity was diagnosed according to World Health Organization criteria using body mass index. Body mass index is defined as a person's weight, in kilograms (kg), divided by the square of height in meters (m), and it is classified as follows:

≤18.49 kg/m2: Under-weight 18.50-24.99 kg/m2: Normal-weight 25.00-29.99 kg/m2: Overweight 30.00-34.9 kg/m2: Obesity class I 35.00-39.99 kg/m2: Obesity class II

≥40.00 kg/m2: Obesity class III (morbid obesity)

Periodontal status was determined through plaque index, gingival index, bleeding on probing, pocket probing depth, clinical attachment level and radiographs. Periodontal status was classified according to criteria proposed by the 1999 International World Workshop for a Classification of Periodontal Disease and Conditions as either 'periodontally healthy', 'gingivitis' or 'generalized chronic periodontitis'. Study participants were then grouped according to body mass index and periodontal status as follows:

Group 1: Group normal weight +periodontally healthy subjects Group 2: Group normal weight + gingivitis subjects Group 3: Group normal weight + generalized chronic periodontitis subjects Group 4: Group obese + periodontally healthy subjects Group 5: Group obese + gingivitis subjects Group 6: Group obese + generalized chronic periodontitis subjects All clinical examinations and gingival crevicular fluid collection were performed by a single examiner. All laboratory procedures were performed by another researcher blinded to the study.

A total of 108 gingival crevicular fluid samples were taken from the Group 5 (18 subjects x 6 sites) and 90 samples from each of the remaining 5 groups (15 subjects per group x 6 sites). All samples were collected between 8-10 am on the day following periodontal status assessment. Samples were collected from the sites in the chronic periodontitis group that fit the following criteria: pocket probing depth≥5mm, clinical attachment level≥5mm and ≥30% radiographic alveolar bone loss. Accordingly, gingival crevicular fluid samples were collected from 2 molar teeth, 2 premolar teeth and 2 incisors. Gingival crevicular fluid samples were collected from the same 6 sites in the gingivitis and periodontally healthy groups in order to maintain consistency of sampling.

Inclusion Criteria:

(i) ≥ 18 years of age and having ≥ 16 teeth; (ii) no periodontal therapy in the 6 months prior to data collection; (iii) no systemic problems or chemotherapy within the 6 weeks prior to data collection; (iv) no previous history of smoking.

Exclusion Criteria:

(i) medical history of cancer, rheumatoid arthritis, diabetes mellitus, or cardiovascular disease; (ii) compromised immune system; (iii) pregnancy, menopause, or lactation; (iv) ongoing drug therapy that might affect the clinical characteristics of periodontitis; (v) use of systemic antimicrobials during the 6 weeks prior to data collection; (vi) dental treatment during the 6 months prior to data collection.

Systemically healthy 45 normal weight adults and 48 class I obese adults