sybraloy and tytin

During mastication, dental amalgams are simultaneously subjected to corrosion by the oral environment and to a sliding-wear process by biting forces. In the present study, the effect of sliding wear on the corrosion behavior of two high-copper dental amalgams was investigated.. An experimental apparatus was utilized that allows electrochemical testing under sliding-wear conditions. Corrosion potential measurements and anodic polarization scans were conducted in 0.1 M NaCl solution under sliding wear to characterize the behavior of two commercial, high-copper, single composition dental amalgams. In addition, long duration tests were conducted to assess possible corrosion and wear synergistic effects.. The results showed that sliding wear caused a sharp reduction in the corrosion potential, a significant increase in the corrosion rate and a decrease in the repassivation rate of both amalgams. These effects are due to the mechanical removal by the wear process of the surface protective film formed on dental amalgams. The simultaneous action of sliding wear and corrosion can also induce embrittlement that leads to cracking.. The present evidence suggests that this cracking may be one of the major contributors to marginal failures of dental amalgam restorations.

Topics: Copper; Corrosion; Dental Alloys; Dental Amalgam; Dental Restoration Failure; Dental Restoration Wear; Dental Stress Analysis; Materials Testing; Microscopy, Electron, Scanning; Surface Properties

Carbamide peroxide (CP) is an easily administered material for whitening teeth. Although toxicological research on CP alone has revealed no adverse health effects, possible oxidation and release of mercury from amalgams have not previously been investigated. This research evaluated the quantitative release of mercury from amalgams into solution by CP. CP preparations can generally be divided into two classes based on the presence or absence of carbopol, an oxygen-releasing inhibitor. Rembrandt (R), a 10% CP with carbopol and White and Brite (WB), a 10% CP without carbopol were used in this study. Four different types of amalgams [Dispersalloy (D), Sybraloy (S), Tytin (T) and Valiant Ph.D. (V)] were selected. Uniform samples of the four amalgams were prepared and stored at 37 degrees C for 1 week. Vials of saline (10 ml), R and WB were prepared. R and WB were mixed with saline to a 50:50 solution to reduce viscosity and facilitate stirring. Magnetic teflon coated stir bars were placed in all vials, and one amalgam specimen was placed in each non-control vial. After being stirred for 8 hours, solutions were analyzed for elemental mercury content using a Jerome Gold Film Mercury Analyzer. All background mercury levels were zero, but following the experiment there were significantly higher amounts of mercury in the CP solutions as compared to the 100% saline solutions. These results suggest there is an active oxidation of the amalgam releasing mercury ions into solution.

Topics: Acrylic Resins; Analysis of Variance; Carbamide Peroxide; Dental Alloys; Dental Amalgam; Drug Combinations; Mercury; Peroxides; Polyvinyls; Regression Analysis; Solubility; Urea

The release of mercury vapor was determined from eleven different amalgams exposed to externally induced corrosion by galvanic contact with a dental casting gold alloy. The electrolyte was an artificial saliva solution at 37 degrees C. The corrosion rates of the amalgams could be divided into two groups corresponding to the grouping into conventional and high-copper materials. The mercury release rate decreased during the 24 h test period for all the amalgams except one containing indium. There was no significant difference in the total mercury release between the conventional and high-copper amalgams as groups. The same applied for the individual products, except the one containing indium, which released significantly more mercury vapor than the two products with the lowest release.

Topics: Analysis of Variance; Copper; Corrosion; Dental Alloys; Dental Amalgam; Electrogalvanism, Intraoral; Gold Alloys; Indium; Mercury; Silver; Statistics, Nonparametric

The effect of width of the restoration, tooth position, and amalgam type on the fracture of the margins of 13- to 14-year-old, high-copper, amalgam restorations was evaluated. The evaluation assessed 193 photographs of restorations by use of ridit analysis and a rank-ordering test. The results indicated that the width of the restoration was the predominant factor and that tooth position and the different high-copper alloys were less significant. Interactions between tooth position and width indicated that lower premolars with conservative restorations exhibited the least fracture at the margins, and upper premolars with a wide preparation exhibited the most. It is postulated that tooth deflection under mastication may play a role in long-term fracture at the margins of amalgams.

Topics: Analysis of Variance; Dental Alloys; Dental Amalgam; Dental Restoration, Permanent; Evaluation Studies as Topic; Humans; Odontometry; Risk Factors; Surface Properties

Topics: Copper; Corrosion; Dental Alloys; Dental Amalgam; Dental Caries; Dental Restoration, Permanent; Humans; Tin

Topics: Copper; Dental Alloys; Dental Amalgam; Elasticity; Stress, Mechanical

A microindentation technique was used to study and estimate the fracture toughness of six amalgams. A significant difference is observed between fracture toughness at the bulk and the margin of amalgams. All amalgams show significant differences in fracture toughness as a function of distance from the margin. Microindentation measurement of fracture toughness appears to be an effective method of evaluating the localized brittleness of amalgams.

Topics: Dental Alloys; Dental Amalgam; Dental Stress Analysis; Hardness Tests

Fracture of the margins is the most common cause of failure of dental amalgam restorations. Both corrosion and creep have been identified as possible contributors to this type of failure. The stresses that induce creep may arise from the continued setting expansion of the amalgam, the formation of corrosion products, mastication, or from the thermal expansion of the amalgam during ingestion of hot foods. The latter two are low-frequency cyclic stresses. The amalgams used in dentistry have fusion temperatures only about 40 degrees C above mouth temperature, and they experience grain boundary sliding during creep deformation. Since grain boundary sliding, low-frequency cyclic stresses, and a temperature near the fusion temperature of the alloy are prerequisites for so-called "creep-fatigue fracture", this type of fracture may contribute to amalgam margin failure. Amalgam made from seven different alloys was condensed into stainless steel dies. After being allowed to set for seven days, the specimens were thermally cycled between 4 degrees C and 50 degrees C for 500 and 1000 cycles. Amalgam margin integrity was evaluated by scanning electron microscopy both before and after each cycling period. The amount of margin fracture was calculated after 1000 cycles. Thermal cycling of amalgam restorations placed in stainless steel dies resulted in predominantly intergranular fracturing of the amalgam margins, indicating that creep-fatigue failure may be a significant contributor to in vivo margin fracturing.

Topics: Chemical Phenomena; Chemistry, Physical; Dental Alloys; Dental Amalgam; Microscopy, Electron, Scanning; Stress, Mechanical; Surface Properties; Temperature

The anodic and cathodic polarization of five dental amalgams were determined as a function of oxygen concentration in Ringer's solution and artificial saliva. The results indicate an anodic polarization behaviour dependent on Cl ion concentration and a corrosion potential determined primarily by oxygen concentration. At high oxygen concentrations the corrosion rates of traditional and copper enriched amalgams were equivalent.

Topics: Copper; Corrosion; Dental Alloys; Dental Amalgam; Electrochemistry; Oxygen; Saliva, Artificial; Sodium Chloride