sybraloy and indiloy

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

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

Topics: Acrylic Resins; Bisphenol A-Glycidyl Methacrylate; Composite Resins; Dental Alloys; Dental Amalgam; Dental Plaque; Dentures; Dietary Carbohydrates; Glass Ionomer Cements; Humans; Polyurethanes; Random Allocation; Research Design; Surface Properties