Background:Pathogenesis of most of the inflammatory process are associated with reactive oxygen species (ROS), derived from various metabolic sources and which may lead to direct or indirect tissue damage due to oxidative stress, resulting in periodontal diseases. Usually antioxidant systems are capable of removing free radicals, thereby preventing tissue damage from free radical. ROS can result in tissue damage, involving lipid peroxidation. The aim of this study was to evaluate and compare the levels of superoxide dismutase (SOD), glutathione peroxidase (GPx), malondialdehyde (MDA), and sialic acid (SA) in periodontally healthy and chronic periodontitis among nonsmokers and smokers and to determine their value as diagnostic markers for chronic periodontitis.Materials and Methods:A total of 90 male patients aged 20--60 years were recruited and grouped as Group 1: 30 Healthy nonsmokers, who had never smoked. Group 2: 30 nonsmokers with chronic periodontitis. Group 3: 30 smokers with chronic periodontitis. Unstimulated saliva was collected for at least 5 min and clinical measurements; SOD, GPx, MDA and SA were assessed using a spectrophotometric method.Results:Data showed a significant correlation between salivary SOD, GPx, MDA, and SA in group 1, group 2, and group 3. SOD and GPx were found to be lower and MDA and SA levels were found to be higher among smokers with chronic periodontitis.Conclusion:Reduced levels of antioxidant enzymes SOD and GPx and elevated levels of lipid peroxidation product MDA as well as increased levels of SA could be used as diagnostic markers to measure oxidative stress in periodontal disease associated with risk factor such as smoking.