This clinical trial aims to evaluate the clinical, biochemical and microbiological efficacy of ozone treatment as an adjunct to nonsurgical periodontal treatment (NSPT) in periodontitis patients. The main question it aims to answer is: • Is the application of gaseous ozone, as an adjunct to NSPT, to periodontal pockets in patients with periodontitis alters the clinical periodontal parameters, gingival crevicular fluid levels of inflammatory cytokines, and periodontal pathogens compared to NSPT alone? The study will be performed according to a split-mouth design, the contralateral quadrants with similar periodontal status in each patient will be randomly allocated to one of the following two different treatment modalities. Participants will be applied NSPT consisting of supra and subgingival debridement. * NSPT will be applied alone in one quadrant * In addition to NSPT, ozone therapy procedures were performed using a device at contralateral sites. Researchers will compare the sites with and without ozone therapy in addition to NSPT to see if ozone therapy adjunct to the NSPT affects clinical, biochemical, and microbiological changes