[Effect of formalin-creosote on the rat periapical tissues after pulpectomy]

The purpose of the present study was to investigate histologically, histometrically and immunohistochemically the effect of formalin-creosote (FC) on the periapical tissues after pulpectomy in rats. Experiment I. Seventy-five rats were divided into 3 groups. In all Groups, the mesial root of the right mandibular first molar was removed. After pulpectomy, in Group A, a paper point containing saline was inserted into the root canal. In Group B, a paper point containing FC was inserted, whereas, in Group C, FC was applied and then a paper point containing FC was inserted. The access cavity was sealed with amalgam. The animals were killed at 1, 3, 7, 14 and 28 days. The periapical tissues were examined histologically. The vertical length and the area of the apical periodontal ligament were measured histometrically. The inflammatory cells and the fibroblasts per unit area in the apical granulation tissue were counted. Experiment II. Eighteen rats were divided into 3 groups. In all Groups, pulpectomy was performed as in the experiment I. In Group a, a paper point containing saline was inserted into the root canal. In Group b, a paper point containing FC was inserted, whereas, in Group c, FC was applied and then a paper point containing FC was inserted. The animals were killed at 14 and 28 days. The presence of macrophages in the granulation tissue was examined using polyclonal antibody to lysozyme immunohistochemical techniques. The results were as follows. Experiment I. Histologically, in Group A, severe inflammation was observed in the periapical tissues at 1 and 3 days. Inflammation became moderate and fibrous tissue proliferation was observed in the periapical tissues at 7 days. Inflammation became slight and fibrous tissue increased at 14 and 28 days. In Group B, severe inflammation was observed in the periapical tissues at 1 and 3 days. Inflammation became moderate at 7 and 14 days. Resorption of alveolar bone was observed after 7 days. Fibrous tissue proliferation and resorption of the apical root were seen after 14 days. Inflammation became slight at 28 days. In Group C, severe inflammation was found in the periapical tissues at 1, 3 and 7 days. Resorption of alveolar bone was seen after 7 days. Moderate inflammation remained and fibrous tissue proliferation was seen at 14 and 28 days. Resorption of the apical root was observed after 14 days. Histometrically, vertical length and area of the apical periodontal ligament in Groups B and C increased significantly compared with those in Group A at 14 and 28 days.(ABSTRACT TRUNCATED AT 400 WORDS)