Inhibition of orthodontically induced root resorption with echistatin, an RGD-containing peptide.

INTRODUCTION Induced dental root resorption is a common side effect of orthodontic treatment. It is an unpredictable phenomenon, and its etiology is unknown. Odontoclasts responsible for the resorption of the dental tissues--ie, cementum and dentin--share many cytochemical and morphological characteristics with osteoclasts, which are responsible for bone resorption. The aim of this study was to explore cellular mechanisms that decrease induced root resorption in orthodontically treated teeth. METHODS The effects of targeting the alphavbeta3 integrin receptor, expressed by odontoclasts, on induced root resorption surface areas and the number of root resorption lacunae were investigated by using an RGD-containing peptide, echistatin. The effect of echistatin on the number of clast cells in the periodontium was also examined. Tooth movement was achieved in 14 Sprague-Dawley rats by placing elastic bands between the right maxillary first and second molars for 24 hours. The animals were equally divided into 2 groups; the experimental animals received echistatin intravenously for 8 hours (0.8 microg/kg/min), and the controls received sterile water. The specimens obtained were processed for light microscopy. The surface area and the number of root resorption lacunae were measured histomorphometrically by using digital photomicrographs. Echistatin labeled with a fluorescent marker was used to confirm its presence in clast cells with fluorescent microscopy. Cytochemically, tartrate-resistant acid phosphatase was used to quantify mature and committed clast cells. Echistatin was localized in targeted cells in the periodontium. RESULTS Echistatin significantly decreased root resorption surface areas (P < .01) and reduced the number of root resorption lacunae (P < .01). There was no statistically significant difference in clast cell numbers. CONCLUSIONS Targeting alphavbeta3 integrin receptor expressed by odontoclasts can be effective in reducing root resorption during tooth movement. Further studies are needed to elucidate the mechanism of this inhibition.