Current study results show that synbiotic mouthwash signif- cantly prevent OM induced by radiotherapy in oral cancer patients. The pathobiology of OM is complex and multifac- eted, and the role of oral microbiota as an efective preven- tive and protective factor seems to be very important [40]. Some studies have shown that despite preventive oral care, patients undergoing cancer treatment developed OM, and the time of onset and the severity of OM were associated with normal oral fora before and during treatment [41]