The protective effect of the curcumin-based oral gel (PerioGold®, Bharma, Perth, WA, Australia) on ROS production in the model of oxidative stress for (A) HOKs, (B) OKF6, (C) DOKs, and (D) PE/CA-PJ15. H2O2 levels; HOKs (341 µM), OKF6 (134.7 µM), DOKs (532.1 µM), and PE/CA-PJ15 (927.8 µM). Low-dose curcumin; HOKs (10 µM), OKF6 (25 µM), DOKs (25 µM), and PE/CA-PJ15 (50 µM). High-dose curcumin; HOKs (25 µM), OKF6 (50 µM), DOKs (50 µM), and PE/CA-PJ15 (100 µM). Statistical significance values represent the difference in comparison with H2O2-induced groups. Statistical significance is defined as follows: * p < 0.05, ** p < 0.002, *** p < 0.0005, **** p < 0.0001.