AIM: To evaluate oxidation and antioxidant activity in the saliva of periodontitis patients following non-surgical periodontal therapy applied either as full mouth subgingival instrumentation (FM) or quadrantwise (Q). METHODS: Patients affected by periodontitis were randomly allocated to receive FM or Q and followed up at 1st and 3rd months. Saliva samples and periodontal variables were collected at baseline, 1st, and 3rd month. The primary outcomes were the total antioxidant status (TAS), total oxidant status (TOS). Secondary outcomes were clinical measurements, Tumour Necrosis Factor alpha (TNF alpha), and Oxidative Stress Index (OSI) parameters. RESULTS: Forty-five subjects were included in the study. Both FM and Q resulted reductions in all periodontal variables, TNF alpha and TOS values, with an improvement in TAS values compared to baseline. Significant differences were observed in the reductions of probing pocket depth (PPD) and clinical attachment level (CAL) between the FM group and the Q group as periodontal variables (p <
0.05). The change in TNF alpha (ng/L) and TAS (mmol Trolox Eq/L) from baseline to post treatment significantly improved in FM group compared to Q. CONCLUSION: Both treatment protocols were efficient in the treatment of periodontitis but the FM therapy significantly reduced periodontal tissue inflammation, as evidenced by changes in both clinical and biochemical parameters in our study. However, it may be seen that FM therapy is more effective during short-term recovery, maybe the reason could be attributed to TAS and TNF alpha changes following FM therapy. TRIAL REGISTRATION: This study was registered at Thai Clinical Trials Registry. ( https://www.thaiclinicaltrials.org/show/TCTR20240416007 , TCTR ID: TCTR20240416007
date of registration: 16 April 2024)-retrospectively registered).