“…For example, local injection of cytokines [ 30 ], glutamate [ [35] , [36] , [37] , [38] ], serotonin [ 39 ], acid saline [ 40 ] and nerve growth factor [ 41 , 42 ] can cause pain and hyperalgesia in the deep craniofacial tissues. These results are consistent with the findings that TMD patients increase experimentally-induced pain sensitivity in the facial areas, in which the level of inflammatory mediators is elevated [ 24 , [27] , [28] , [29] , [30] , [31] , [32] , [33] , 43 , 44 ].…”