tytin and stannic-oxide

Previous studies have investigated the electrolytic action of oral electrogalvanism. However, the reasons why certain treatments or materials are successful in reducing galvanic current have not been addressed fully. This study assessed galvanic current with several materials, surface conditions and treatments.. The authors measured galvanic currents between a type 3 cast gold alloy and Dispersalloy Dispersed Phase Alloy (zinc) (Dentsply Caulk, Milford, Del.) under different surface conditions using a zero-resistance-ammeter technique in a synthetic saliva solution for 10 hours. In addition, the galvanic currents between the same gold and Tytin alloy (non-zinc) (Kerr, Orange, Calif.), experimental zinc alloy (same makeup as that of Tytin, with the addition of zinc) and non-zinc dispersed-phase experimental alloy (essentially the same physical and chemical makeup as that of Dispersalloy, with the exclusion of zinc) were measured. Triplicate tests were performed for each condition.. The statistical analysis indicated that electrogalvanic activity is reduced significantly when the amalgam surface is treated with tin oxide or silver nitrate. Both zinc-containing amalgams in their as-carved condition exhibited higher anodic charge densities than did their zinc-free counterparts. Galvanic current measured in Dispersalloy was reduced with the passage of time after carving.. Galvanic interaction between cast gold and amalgam is reduced with time and surface treatments, but is increased considerably when the amalgam contains zinc.. Amalgam restorations containing zinc that are in contact with gold restorations occasionally elicit galvanic pain. Selection of a non-zinc-containing amalgam will reduce the level of galvanic interaction. Galvanic pain from occlusal contact is reduced or eliminated when the restoration is brushed with tin oxide immediately after carving or is treated with 2 percent silver nitrate. Some patients may benefit from having their teeth separated with nonconducting rubber dam material.

Topics: Analysis of Variance; Dental Alloys; Dental Amalgam; Electric Conductivity; Electrogalvanism, Intraoral; Gold Alloys; Humans; Materials Testing; Potentiometry; Saliva, Artificial; Silver Nitrate; Surface Properties; Time Factors; Tin Compounds; Zinc

Dissolution of mercury from dental amalgam has been shown to be diminished by the formation of a tin oxide film on the surface of the mercury-rich gamma 1 phase (Marek, 1990b). Since tin oxides dissolve at low pH values (Deltombe et al., 1974), acidic conditions in the oral cavity may cause an increase in the mercury release. The purpose of this study was to determine the effect of acidity in the range of pH 1 to pH 8 on the rate of mercury dissolution in synthetic saliva from tin-free and tin-containing gamma 1 phase and two commercial dental amalgams. The tested hypothesis was that pH affects mercury dissolution only when a protective oxide film dissolves in an acidic environment. After exposures of the specimens for 2 hr or 24 hr in sealed glass bottles, the solutions were analyzed by flameless atomic absorption spectrophotometry for mercury and silver. The results have shown pH-independent mercury dissolution in the range of pH 3 to 8, and a much faster dissolution at pH 1. At all pH values, more mercury dissolved from the tin-free phase than from the tin-containing phase, and the rate of dissolution was lowest for the dental amalgams. The results were affected by the length of the test exposure. The pH independence in a wide range of pH values has been attributed to the atomic mechanism of mercury dissolution. The low rate of mercury dissolution from specimens containing tin has been explained by the formation of a barrier tin oxide film, which dissolved only at the lowest pH. Dissolution of silver at low pH values is believed to have accelerated dissolution of mercury from the tin-free gamma 1 phase. Variation of the dissolution rate with concentration of the dissolved species and kinetics of oxide film dissolution caused the effect of the exposure period.

Topics: Analysis of Variance; Corrosion; Dental Alloys; Dental Amalgam; Hydrogen-Ion Concentration; Materials Testing; Mercury; Saliva, Artificial; Solubility; Spectrophotometry, Atomic; Statistics, Nonparametric; Tin Compounds; Volatilization