[Histopathological study of the effect of pure metals to the periodontal tissues]

In order to investigate biocompatibility of pure metals, which are widely used, the gingival tissues were brought into contact with pure metals. Nine kinds of pure metals, such as gold, platinum, silver, palladium, copper, nickel, zinc, indium and tin were used in the analysis of biocompatibility. With a No. 1/2 round bar, a standardized small cavity was prepared in the mesiolingual cervical portion of the upper first molar. Nine kinds of pure metals powder were inserted into the small cavity of the maxillary root surface in rats. Post operative changes of the gingival tissue were studied histopathologically. The results were as follows: 1. Gold, palladium and indium powder were observed in the lamina propria of the gingiva. Infiltration of cells was not observed around these pure metal powders. Gold, palladium and indium powders showed little cytotoxicity. 2. Zinc powders were not associated with chronic inflammatory charges. Zinc powders were surrounded by an abundance of connective tissue substances. The fragments were surrounded by collagen fibers, but no inflammatory cells were present. Zinc powders showed little cytotoxicity. 3. Platinum and tin powders were not associated with chronic inflammatory changes. These pure metal powders were surrounded by macrophages, but no other mononuclear inflammatory cells were present. 4. Clumps and granules of silver powder were not associated with chronic inflammatory changes. Multinucleate giant cells were shown surrounding silver powders. Silver powders were observed to have been taken into the multinucleate giant cells. Many of these cells also contained fine dark granules in their cytoplasm, and a few contained small pieces of silver. The tissue reaction to silver showed little cytotoxicity. 5. Copper and nickel powders were associated with chronic inflammatory cells. Moderate chronic inflammation and occasional neutrophils leucocytes and lymphocytes were shown to be associated with these pure metal powders. Copper and nickel caused extensive damage to the gingival tissues.