A histologic comparison of Hydron and zinc oxide-eugenol as endodontic filling materials in the primary teeth of dogs.

Currently available endodontic filling materials for primary teeth demonstrate several inadequacies. Therefore, this study histologically evaluates Hydron (2-hydroxyethylmethacrylate) and zinc oxide and eugenol (ZOE) as primary tooth endodontic filling materials in dogs to compare the materials' biocompatibility and to determine whether they undergo resorption in a physiologic manner. Primary molars of six mongrel dogs, 2 to 3 months old, received one-step endodontic therapy. By random selection, two thirds of the molars were filled with either Hydron or ZOE and the remainder were used as unoperated controls. Block sections taken during physiologic root resorption were used to obtain serial hematoxylin and eosin sections of periapical regions. Hydron was phagocytosed by mononuclear macrophages in a physiologic manner and at a rate comparable to that of root tissues. In contrast, ZOE demonstrated delayed resorption and transitory inflammation. Neither material showed cytotoxicity. Hydron may therefore be a suitable endodontic material for human primary teeth.