Morphological and functional properties of odontoclasts on dentine resorption

Abstract

Tooth root resorption in tooth movement is the principal unsolved problem in orthodontics. In order to study this mechanism, odontoclasts in bovine deciduous tooth root-resorbing tissues (RRT) were cultured and characterized for their biological properties in comparison with those of osteoclasts. Multinucleated cells isolated from the RRT had tartrate-resistant acid phosphatase activity and responded to calcitonin and also formed the resorption lacunae on the dentine. These results are consistent with the notion that odontoclasts resemble osteoclasts with respect to enzyme-cytochemical and morphological properties. However, odontoclasts cultured on dentine in the presence of 1 alpha,25-dihydroxyvitamin D3 demonstrated a higher activity in forming resorption lacunae than did osteoclasts. Immunohistochemical examinations revealed that interleukin-1 (IL-1) was detected in mononuclear cells and occasionally in odontoclasts that were present adjacent to the site where active root resorption occurred. The IL-1 stimulated the formation of resorption lacunae on dentine to a higher extent in odontoclasts than in osteoclasts, suggesting functional differences between odontoclasts and osteoclasts. In conclusion, the present study demonstrates that 1) odontoclasts present in the RRT possess similar biological properties to those of osteoclasts. However, under certain circumstances odontoclasts may behave differently from osteoclasts; 2) IL-1 produced in the RRT might play a role in controlling the function of odontoclasts in a paracrine and autocrine fashion.