valiant-phd and tytin

Fundamental in vitro wear tests are important for the study of wear mechanisms, provision of data during material development and screening of materials prior to clinical trials. The aim of this project was to compare the wear of six dental restoratives using the BIOMAT wear simulator which was developed to simulate jaw movements and stresses generated in the occlusal contact areas during the chewing process. The correlation of wear to hardness of the restoratives was also assessed. Wear ranking from the least to the most volumetric wear was as follows: high copper unicompositional alloy, Tytin (T) < high copper admixed alloy, Valiant PhD (V) < microfilled composite resin, Silux Plus (S) < gallium alloy, Galloy (G) < heavily filled composite resin, Z100 (Z) < hybrid composite resin, P50 (P). The high copper amalgam alloys had significantly greater wear resistance when compared with all the composite resins. The gallium alloy, microfilled and heavily filled composite resins also exhibited significantly less wear than the hybrid resin. Wear ranking with the BIOMAT simulator was similar to that obtained in vivo. Ranking from the hardest to softest material: high copper unicompositional alloy, T < gallium alloy, G < high copper admixed alloy, V < hybrid composite resin, P < heavily filled composite resin, Z < microfilled composite resin, S. The amalgam alloys were significantly harder than the heavily filled and microfilled composite resins. There was no apparent correlation between wear performance and material hardness.

Topics: Bisphenol A-Glycidyl Methacrylate; Bite Force; Composite Resins; Copper; Dental Alloys; Dental Amalgam; Dental Materials; Dental Restoration Wear; Dental Restoration, Permanent; Equipment Design; Gallium; Hardness; Humans; Mandible; Mastication; Materials Testing; Silicon Dioxide; Stress, Mechanical; Zirconium

Different formulations of amalgam have physical properties that may make them behave differently in the often-contaminated root end environment. Five different brands of amalgam were evaluated for microleakage of root-end fillings placed in extracted human teeth. These included a zinc-free spherical amalgam, a zinc-free admixture amalgam, two zinc-containing admixture amalgams, and a zinc-containing lathe-cut amalgam. The amalgams were placed either into dry root-end preparations or into preparations contaminated with human blood. The fluid filtration method was used to measure microleakage at 1, 2, 4, 8, 12, and 24 wk after placement. Analysis of variance revealed significant differences in the rates of microleakage at every measurement period. Scheffé's test showed that the zinc-free spherical amalgam had significantly greater leakage than all the other products evaluated. There were no significant differences between any of the other products. Blood contamination did not adversely affect the seal of any amalgam.

Topics: Analysis of Variance; Dental Alloys; Dental Amalgam; Dental Leakage; Evaluation Studies as Topic; Humans; Retrograde Obturation; Root Canal Filling Materials; Zinc

Compressive strength, dimensional change during hardening and residual mercury content of three high-copper spherical particle amalgams (Tytin, Logic and Valiant), two admix amalgams (Dispersalloy and Permite C) and a conventional lathe-cut amalgam (New True Dentalloy) were determined as a function of condensation pressure and trituration time. The properties of the three amalgams containing non-spherical particles were markedly dependent on condensation pressure in the range 3 MPa to 14 MPa. Specimens condensed at 3 MPa showed substantially lower strength, greater expansion during hardening and higher residual mercury contents than did specimens condensed at 14 MPa. The three high-copper spherical particle amalgams, on the other hand, were comparatively insensitive to condensation pressure. Variations in trituration time between 5 and 12 seconds had little effect on the properties of any of the amalgams.

Topics: Copper; Dental Alloys; Dental Amalgam; Materials Testing; Mercury; Particle Size; Pressure

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

Palladium-containing amalgam alloys were developed utilizing the atomization method. Single-compositional type alloys were fabricated and palladium was substituted for silver in concentrations up to 5 w/o. Alloy powder with a particle size of less than 45 microns was collected and triturated with mercury. Creep, compressive strength and dimensional change tests were performed according to ADA Specification No. 1 along with controls of Tytin, Valiant and Valiant-Ph.D. Values for creep decreased and compressive strength increased markedly with additions of palladium. Current densities of the experimental amalgams containing palladium were determined to be an order of magnitude less than the original amalgams in the electrochemical test. A trend of positive relationships between properties and palladium additions was indicated.

Topics: Corrosion; Dental Alloys; Dental Amalgam; Materials Testing; Palladium; Tensile Strength