Remarkably, the group submitted to control mechanical trauma showed no sign of inflammation (MPO: 1.4±0.4 U/mg of tissue; TNF-α: 354.3±354.3 pg/mg of tissue; IL-1β: 691.3± 239.5 pg/mg of tissue) compared with the saline group (P>0.05, Figure 4A-C), indicating that the scratch was not enough to cause oral mucositis. Here, MPO is linked to oral mucositis.