Nitro-oxidative Stress in Periodontitis

Introduction:

Teeth and their supporting periodontal structures are of great importance in good oral health. Periodontitis is an inflammatory disease of the periodontium which affects the supporting tissues of the teeth. The disease is multifaceted and its etio-pathogenecity is still not fully understood and therefore the treatment of different types of periodontal disease can be very difficult. Numerous risk factors have been implicated in the disease process including risk determinants and risk indicators. Most recently, strong body of evidence has accumulated to support a role for reactive oxygen (ROS) and nitrogen species (RNS) either as trigger agents or more frequently, aggravators of the primary lesions in periodontitis.

Oxygen and nitrogen reactive species are involved in a large number of physiological and pathological processes. ROS generated by monocytes and neutrophyles during inflammation are important aggression factors in the periodontal tissues. ROS play an important role in activation of osteoclasts and in bone resorption.

Oxidative stress is a condition arising when there is a serious imbalance between the levels of free radicals in a cell and its antioxidant defenses in favor of the former. Thus, tissue damage can result when antioxidant systems are unable to counteract the free radicals actions efficiently. Inflammation when stimulated by bacterial pathogens, host cells release proinflammatory cytokines (IL-1α, IL-6, IL-8, and tumor necrosis factor-α) as part of immune response. These cytokines recruit polymorphonuclear cells (PMNs) that play a major role in the etiology of periodontal disease by producing proteolytic enzymes, such as elastase and O2 (molecular oxygen) by the oxidative burst.

In a recent study, Abou Sulaiman \& Shehadeh found that serum total antioxidant capacity (TAS) was lower in non-smokers Syrian patients with chronic periodontitis compared to healthy controls. Also, they reported that periodontal treatment restored TAS levels to normal levels similar to healthy controls.

The aim of this study is to assess the levels of ROS and RNS in serum and gingival crevicular fluid (GCF) samples taken from periodontitis patients (chronic and aggressive) and healthy controls. Subsequently, correlating these levels with severity of periodontal disease in Syrian patients.

Materials and methods:

A total of 80 subjects will be invited to participate in this study from the patients referred to the Department of Periodontology, Faculty of Dentistry, University of Damascus. The study has been approved by our local Review Board. Subjects will be recruited according to specific inclusion criteria after completion of medical and dental history questionnaires. Patients will sign a consent form after being advised about the nature of the study.

The selection of patients will be made according of the criteria approved by the 1999 international world workshop for a classification system of periodontal diseases and conditions using five clinical parameters and full mouth or panoramic radiographs for diagnosis.

Subjects will be allocated into four groups:

• Chronic Periodontitis group (ChP): comprise 20 patients aged > 45 years and have presence of ≥2 non-adjacent sites per quadrant that were not first molars or incisors, with probing depth (PD) ≥5 mm, which bleed on gentle probing. The demonstrated radiographic bone loss ≥30% of the root length, patient with poor oral hygiene, the amount of accumulated plaque commensurate with the amount of clinical attachment level (CAL)
• Resistant Control group (R): comprise 20 age-sex matched patients who are > 45 years exhibit no signs of periodontal disease as determined by the absence of the evidence of interproximal (CAL ≤ 1mm), PD > 3 mm at any site, whole-mouth bleeding scores <10% and have no clinical signs of gingival inflammation .
• Aggressive Periodontitis group (AgP): comprise 20 patients who are aged < 35 years and diagnosed with rapid attachment loss with periodontal pocket depth (PD) > 4 mm around at least three teeth other than the first molars and incisors. Rapid bone destruction (>50%bone loss at diseased sites). Weak relationship between dental plaque and the severity of gingival inflammation.
• Young Control group (YC): comprise 20 age- and sex matched patients who are < 35 years and exhibit no signs of periodontal disease.

Clinical measurements:

A standard periodontal probe will be used for recording periodontal indices at six sites per tooth. The examined clinical parameters include bleeding on probing (BOP), plaque index (PI), clinical attachment loss (CAL) and periodontal pocket depth (PPD) and gingival index (GI).

Collection of samples

Subjects will be asked to refrain from brushing within 1 hour of sampling. (GCF) samples will be obtained using standard paper strips (Periocol strips, Oraflow, NY, USA). 6 samples from each individual (mesiofacial, distopalatal) sites from each examined tooth (incisor, premolar and molar) in the maxilla (Chapple et al. 2002). Strips will be put in PBS Buffer solution for 30 minutes then extracted and stored under liquid nitrogen.

Venous blood samples will be collected from the antecubital fossa and stored in lithium heparin tubes and allowed to stand for 30 minutes before being centrifuged at 1000 ×g for 30 minutes, samples will be aliquoted into cryogenic vials and will be stored under liquid nitrogen.

Laboratory studies:

• TBARS assay (HPLC) will be used to assess the malondialdihyde levels as a marker of oxidative stress.
• Griess reagent to assess nitric oxide levels as a marker of nitrosative stress.