Determination of RNA/DNA Damage Associated With Oxidative Stress in Periodontitis Patients

Periodontitis is a chronic inflammatory disease that leads to the progressive destruction of the tooth-supporting tissues. Oxidative stress plays a central role in its pathogenesis, as excessive production of reactive oxygen species (ROS) can damage cellular structures, including lipids, proteins, and nucleic acids. Among oxidative stress-related biomarkers, 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 8-hydroxyguanosine (8-OHG) are widely recognized indicators of DNA and RNA damage, respectively. These biomarkers reflect the biochemical consequences of oxidative stress and are increasingly used to evaluate host responses in periodontal disease.

Cigarette smoking is one of the strongest environmental risk factors for periodontitis and is known to enhance oxidative stress through multiple mechanisms. However, the combined effect of smoking and advanced periodontitis on salivary oxidative DNA and RNA damage has not been fully clarified. Assessing both 8-OHdG and 8-OHG simultaneously may provide deeper insight into the molecular pathways linking smoking, inflammation, and periodontal tissue destruction.

This study was designed to evaluate salivary levels of oxidative nucleic acid damage in individuals with Stage III periodontitis who smoke or do not smoke, as well as in periodontally healthy controls. The study also aimed to investigate the relationship between these biomarkers and clinical periodontal measurements. By examining DNA and RNA oxidation together, the study sought to provide a multidimensional understanding of the host oxidative response in periodontitis.

All participants underwent full-mouth periodontal examination performed by a calibrated clinician. Unstimulated saliva samples were collected under standardized morning conditions, processed by centrifugation to remove cellular debris, and stored at -80°C until biochemical analysis. Levels of 8-OHdG and 8-OHG were quantified using a high-sensitivity ELISA method capable of detecting multiple oxidized guanine derivatives.

Biochemical findings demonstrated that oxidative DNA and RNA damage levels were higher in individuals with periodontitis compared to healthy controls, with smokers exhibiting the highest levels overall. Oxidative biomarker levels showed positive correlations with key periodontal parameters, including probing depth, clinical attachment loss, plaque accumulation, gingival inflammation, and bleeding on probing. These results suggest that the inflammatory burden of periodontitis amplifies oxidative stress at the nucleic acid level and that smoking contributes an additional biological load.

In addition to biochemical assessment, buccal mucosa samples were evaluated cytologically using hematoxylin and eosin staining. All specimens showed adequate cellularity, and no significant differences in epithelial dysplasia were observed across study groups. This may be related to the predominance of superficial epithelial cells in the collected samples.

Overall, this study provides an integrated biochemical and cytomorphological assessment of oxidative stress in periodontitis. The findings support the potential use of salivary 8-OHdG and 8-OHG as non-invasive biomarkers for disease monitoring and contribute novel evidence regarding the interaction between smoking, oxidative stress, and periodontal inflammation.

Inclusion criteria

• Individuals aged 18 years or older
• Having at least 16 permanent teeth, excluding third molars
• Not using orthodontic appliances
• Not pregnant or breastfeeding
• Systemically healthy individuals with no systemic diseases that could affect periodontal status
• No use of anti-inflammatory or antimicrobial medications within the last 6 months
• No periodontal treatment within the last 12 months

Exclusion criteria

• Pregnant or breastfeeding individuals.
• Use of anti-inflammatory or antimicrobial drugs in the past 6 months.
• Use of antioxidant supplements in the past 3 months.
• Periodontal treatment within the past 12 months.
• Diagnosis of psychiatric disorders.
• Any oral infection.
• Fewer than 16 permanent teeth (excluding third molars).
• Alcohol dependence.
• Active infectious diseases (Acute hepatitis, AIDS, tuberculosis), malignancy, or any systemic condition that may affect periodontal tissues.
• Current use of medications known to affect periodontal tissues (phenytoin, cyclosporine A, calcium channel blockers).