RANK, RANKL and OPG expressions in a permanent molar with a replacement resorption

[Abstract] The aim of this study was to explore the expression of RANK, RANKL and OPG during ankylosis. Structural details and immunohistochemical investigations of the expression of RANK, RANKL and OPG in an extracted secondary retained permanent molar of a 12-year-old girl are reported. Woven and lamellar bones were observed in the thickness of the remodeled dental wall and a tertiary dentin was noticed around the pulp cavity. The resorbing multinucleated cells expressed TRAP and RANK but few of them also expressed RANKL. Both odontoblasts and osteoblasts expressed TRAP and RANK, but the expression of RANKL was limited to osteoblasts. OPG remained undetected. The present case reveals unusual expression of RANKL in the resorbing cells, TRAP and RANK in both osteoblasts and odontoblasts, and a failure of detection of OPG. These proteins could be involved in the pathogenesis of tooth ankylosis.