"Long distance" action of parachlorophenol and formalin in polyethylene tubes implanted in guinea pigs

Two endodontic intracanal medicaments (parachlorophenol and formalin) in polyethylene tubes were tested for their irritant effect by implantation in the backs of guinea pigs. Histologic evaluation at 3 days showed an exudate with polymorphonuclear leukocytes in the open part of the tube. At 10 days most of the tubes showed fibroblast migration into the open lumen, with necrotic tissue trapped between the fibroblast migration and the exudate. At 90 days only a little fibroblast migration was found in all of the tubes. No necrotic tissue was trapped and no irritation was seen. No difference could be observed between the reaction in the experimental and the control situations.