Evaluation of the Impact of Alveolar Bone Resorption on the Root Formation of Molars in Transgenic Mice with RANK Over-expression

Alterations in the balance of the osteoblastic-osteoclastic activity (osteopetrosis, osteolysis) have an impact on the dental development. The over activation of the osteoclastogenesis pathway RANK/RANKL/OPG in RANK mice produces an acceleration of tooth eruption and root elongation, suggesting this pathway could control the speed of tooth formation. Evaluate the effect of osteoclastic hyperactivity on the root formation of molars in RANK mice. Histologic study both descriptive and comparative of the impact of hyper-resorption of the alveolar bone in Hertwig's epithelial root sheath (HERS) of molars in both RANK mice and controls. This is done through the immuno-detection of matrical, epithelial and cellular proliferation proteins with histological, histoenzymology and inmunohistochemical techniques. Osteoclastic hiperactivity in alveolar bone does not alter the root structure and integrity of molars in RANK mice; the acceleration in root formation does not alter the HERS integrity. An area of cellular hyper-proliferation in the apical follicular tissue of HERS was found, which could regulate root growth in response to osteoclastic activity. The overexpressed RANK produces an inhibition of amelogenin expression at 5 days of age, suggesting an indirect regulation of these cells by RANK/RANKL. Exploring other molecular factors expressed in HERS, and the related engram, would make possible the use of new therapies for the control of osseous and inflammatory pathologies during root formation.