Crevice Corrosion Products of Dental Amalgam E.J. SUTOW, D.W. JONES, G.C. HALL, and C.G. OWEN Division of Dental Biomaterials Science, Faculty of Dentistry, Dalhousie University,
The objective of this study was to determine the in vitro corrosion products that resulted from crevice corrosion of lowand high-copper dental amalgams. Specimens were potentiostatically polarized in a chloride-containing electrolyte while set against a PTFE surface to form a crevice. After 16 h, corrosion products were examined by light microscopy, SEM, EDS, and XRD. Analysis showed the presence of three previously reported products [Sn4(OH)6CI2, SnO, and Cu2O] and a new product, CuCI, which formed on high-copper, 'y2-free amalgams. Thermodynamic considerations show that CuCl is stable for the reported in vivo potentials of amalgam ,restorations and the high acidity and high chloride ion concentration associated with crevice corrosion. J Dent Res 70(7):1082-1087, July, 1991
Introduction. Dental amalgam is believed to deteriorate due to occluded or crevice corrosion conditions on the surface of the restoration and at the restoration-tooth interface (Marek et al., 1973; Sarkar, 1978). The electrolyte in an active amalgam crevice will increase in hydrogen and chloride ion concentrations, relative to the bulk solution, as shown for a model crevice in vitro (Marek and Hochman, 1975). Since the crevice solution composition differs substantially from that of crevice-free corrosion, corrosion products may also differ. The study of corrosion products has focused primarily on in vitro crevice-free corrosion and retrieved restorations. Examination of in vitro specimens shows the formation of various compounds, including SnO, SnO2, Sn4(OH)6CI2, Cu2O, and CuCl2 * 3Cu(OH)2 (Otani et al., 1973; Marshall and Marshall, 1980; Brune, 1981; Marshall et al., 1982; Lin et al., 1983a,b). Retrieval studies show SnO, SnO2, and Sn4(OH)6C12 (Mateer and Reitz, 1970; Marshall and Marshall, 1980; Marshall et al., 1987). These products have been found on the surface and within pores of the restoration, and at the amalgam-tooth interface. The number of in vitro crevice corrosion studies is limited. Marek and Hochman (1974) reported finding a mixture of tin oxide and tin hydroxide in the entrances of model crevices formed with low-copper amalgams. Sarkar et al. (1976) contrasted the effects of surface and interface corrosion of lowcopper amalgam. They reported that surface corrosion led to the formation of mainly tin-rich cuboid-shaped crystals-which were assumed to be tin oxides or hydroxides-while interface corrosion led to the formation of tin- and chlorine-containing rod-like products-which were assumed to be tin oxychloride. Katan and Ryge (1979) crevice-corroded one high-copper, Y2free amalgam and two low-copper amalgams. From their results, they suggested that a SnO hydrate is formed, SnO xH2O (1
The objective of this study was to determine the in vitro corrosion products that resulted from crevice corrosion of lowand high-copper dental amalgams. Specimens were potentiostatically polarized in a chloride-containing electrolyte while set against a PTFE surface to form a crevice. After 16 h, corrosion products were examined by light microscopy, SEM, EDS, and XRD. Analysis showed the presence of three previously reported products [Sn4(OH)6CI2, SnO, and Cu2O] and a new product, CuCI, which formed on high-copper, 'y2-free amalgams. Thermodynamic considerations show that CuCl is stable for the reported in vivo potentials of amalgam ,restorations and the high acidity and high chloride ion concentration associated with crevice corrosion. J Dent Res 70(7):1082-1087, July, 1991
Introduction. Dental amalgam is believed to deteriorate due to occluded or crevice corrosion conditions on the surface of the restoration and at the restoration-tooth interface (Marek et al., 1973; Sarkar, 1978). The electrolyte in an active amalgam crevice will increase in hydrogen and chloride ion concentrations, relative to the bulk solution, as shown for a model crevice in vitro (Marek and Hochman, 1975). Since the crevice solution composition differs substantially from that of crevice-free corrosion, corrosion products may also differ. The study of corrosion products has focused primarily on in vitro crevice-free corrosion and retrieved restorations. Examination of in vitro specimens shows the formation of various compounds, including SnO, SnO2, Sn4(OH)6CI2, Cu2O, and CuCl2 * 3Cu(OH)2 (Otani et al., 1973; Marshall and Marshall, 1980; Brune, 1981; Marshall et al., 1982; Lin et al., 1983a,b). Retrieval studies show SnO, SnO2, and Sn4(OH)6C12 (Mateer and Reitz, 1970; Marshall and Marshall, 1980; Marshall et al., 1987). These products have been found on the surface and within pores of the restoration, and at the amalgam-tooth interface. The number of in vitro crevice corrosion studies is limited. Marek and Hochman (1974) reported finding a mixture of tin oxide and tin hydroxide in the entrances of model crevices formed with low-copper amalgams. Sarkar et al. (1976) contrasted the effects of surface and interface corrosion of lowcopper amalgam. They reported that surface corrosion led to the formation of mainly tin-rich cuboid-shaped crystals-which were assumed to be tin oxides or hydroxides-while interface corrosion led to the formation of tin- and chlorine-containing rod-like products-which were assumed to be tin oxychloride. Katan and Ryge (1979) crevice-corroded one high-copper, Y2free amalgam and two low-copper amalgams. From their results, they suggested that a SnO hydrate is formed, SnO xH2O (1
