Periodontitis group, GSH (373.04 ± 287.42 μmol/L), GPx (92.99 ± 74.40 mU/mL), LPO (0.66 ± 0.36 μmol/L) Subsequent study:  Periodontitis group before treatment, GSH (353.59 ± 141.93 μmol/L), GPx (96.50 ± 35.14 mU/mL), LPO (0.63 ± 0.49 μmol/L); Periodontitis group after treatment, GSH (602.92 ± 170.15 μmol/L), GPx (99.34 ± 45.72 mU/mL), LPO (0.41 ± 0.26 μmol/L). This evidence concerns the gene LPO and periodontitis.