This cross sectional study designed a multiple regression method looking at the effect of conventional risk factors (gender, education, smoking status, alcohol consumption, betel consumption); oral health behavior (tooth cleaning frequency, auxiliary tooth cleaning tools types, and dental visit patterns); and salivary oxidative stress biomarkers (Cu-Zn SOD, MnSOD, PRX2, TRX1 and Catalase) on the clinical periodontal parameters (PI, BOP, and PD mean) in periodontitis patients. This evidence concerns the gene CAT and periodontitis.