Gingival pigmentation due to prolonged retention of metal fragments

This report describes human gingival tissue reaction to prolonged retention of metal fragments which caused localized gingival pigmentation. Pigmented gingival tissues of the palatal gingiva and the mesial interdental papilla around the left maxillary first molar, which was restored with a cast core of silver alloy metal and a metal crown 6 years previously, were investigated with light, electron and electron probe microscopy. Even 6 years later, many black or dark brown deposits of various sizes were observed in the lamina propria mucosae of the patient's gingival tissue. Electron-dense fine particles were observed within the cytoplasm of the fibroblasts. Macrophages containing the electron dense particles were occasionally observed. Examination by electron probe microscopy also revealed silver sulfate, tin sulfate, and iron in the deposits. Fine dust-like particles were also observed in the intercellular space of the gingival epithelium and the pinocytotic vesicles within the epithelial cells in which iron was also detected. Iron seemed to originate from a cutting steel instrument, since it is not a component of silver alloy. It appeared to be excluded by the cellular turnover. However, silver and tin were not detected in the epithelial cells or in the intercellular spaces. It was concluded that the gingival pigmentation caused by embedding of metal fragments would remain permanent, and not be diminished by cellular turnover.