Histopathologic and bacterial evaluation of conventional and new copper amalgams

In vivo pulpal responses in monkeys and in vitro bacterial inhibition studies were completed on new copper amalgams, Sybraloy, Dispersalloy, Tytin and a conventional Spheraloy amalgam. Amalgams were placed in cavities lined with ZOE and in unlined cavities. Silicate and ZOE were used as controls. A total of 165 adult monkey teeth were evaluated at 3 days, 5 and 8 weeks. At 3 days the pulpal responses elicited by the copper amalgams appeared similar to conventional Spheraloy, all showing a slight to moderate response. At 5 weeks the majority of amalgams exhibited a slight pulpar response with a tubular reparative dentin under each restoration. The 8 week pulpal response showed a reduction of the inflammatory response characterized by a tubular reparative dentin with a uniform zone of predentin. Lined ZOE controls exhibited a slight response while silicate showed a moderate response with some persistent chronic inflammation. In vitro bacterial tests revealed that the various amalgams had little to no inhibitory effect on the three serotypes of S. mutans that are most prominent in humans.