A bstract:In this study, we have investigated the effects of HEBP on alveolar bone remodeling and molar tooth development of new born rats especially with regard to the relation of the mineralization rate and tooth eruption. New born rats (3 to 5 days after birth) were injected with 10 mg/kg body weight HEBP subcutaneously every day except Sunday. Mandibles were investigated radiologically and histologically. The mineralization rate of alveolar bone and dentin was assessed by energy-dispersive Xray (EDX) analyis. Soft X-ray radiography disclosed the failure of the first molar tooth eruption, and histological findings showed ankylosis of alveolar bone and tooth root, and dentin resorption by multinucleated giant cells. The result of EDX analysis revealed hypo-mineralization of alveolar bone and normal mineralization of dentin. These data suggest that preosteoclasts might be recruited at the site of alveolar bone and tooth germ interface but could not differentiate into bone-resorbing mature osteoclasts because of hypo-mineralization of alveolar bone.