TNFSF11 and vitamin D deficiency: Anderson and colleagues (2009) reported the development of osteopenia in vitamin D–deficient rats associated with the increased osteoclast surface (Oc.S) in femurs and vertebral bones.(37) The increased ratio of steady-state mRNA levels of RANKL over osteoprotegerin (OPG) in femur bone marrow of vitamin D–deficient rats has been postulated to be responsible for the increased osteoclastogenesis.(37) In our study, the introduced vitamin D deficiency similarly may contribute to the increased osteoclastogenesis during tooth extraction wound healing.