TNFSF11 and periodontitis: Prostaglandins [30, 31] as well as leukotrienes [48, 49] have been shown to be important autocrine and paracrine mediators of mechanical (orthodontic) strain, leading to increased synthesis of proinflammatory cytokines such as IL-1, IL-6—as shown in our study—and chemokines such as IL-8 [50–52], attracting lymphocytes from peripheral blood [53], which are the primary sources of RANK-L in periodontitis [54].