The ultrastructure of copper amalgam-covered dentin from human deciduous teeth

The structure of dentin subjacent to Cu-amalgam restorations was studied. The restorations had been inserted 7-8 years before extraction of the teeth. No lining had been applied. The dentin subjacent to the restorations had a greenish-grayish discoloration, and in the pulpal end irregular secondary dentin had formed. Energy-dispersive X-ray microanalysis of areas showing discoloration confirmed the presence of Cu. Semithin and ultrathin undemineralized sections were studied. Vital pulp tissue and irregular secondary dentin were observed. Close to the predentin and halfway into the dentin most of the dentinal tubules were occluded. In the control material only an occasional occluded tubule was seen. Close to the Cu-amalgam restoration some tubules were occluded or partly occluded, and some were open. The odontoblasts had responded to the irritating agent by obturation of the tubules, thus reducing the permeability of the dentin. Furthermore, irregular secondary dentin had formed in another attempt to wall off the irritating agent.