epoque-80 and tytin

In this study the rate of dissolution of mercury from two dental amalgams with different compositions and structures was determined in vitro under different oxidation and abrasion conditions, and the results were correlated with the electrochemical characteristics.. A spherical high copper and a lathe-cut very high-copper amalgam were tested in aerated and deaerated artificial saliva. The electrochemical characteristics were determined by potential-time, anodic polarization, polarization resistance and cathodic stripping measurements. Mercury release tests were performed after either stabilization in the solution, or abrasion using SiC papers or rotary toothbrush, with or without toothpaste. Dissolved mercury was determined by atomic absorption spectrophotometry.. Both amalgams exhibited passivation, the amalgam with the higher copper content passivating spontaneously even when the oxygen content in the solution was minimized. At a higher oxygen content in the solution the rate of mercury release from the amalgams was lower than when the oxygen content was minimized, and decreased further after a pre-exposure. Brushing generally increased the release.. The results show the importance of the oxidation conditions and passivation characteristics of dental amalgams for mercury release, especially in the transient state after abrasion by chewing or tooth brushing.

Topics: Dental Alloys; Dental Amalgam; Electrochemistry; Mercury; Spectrophotometry, Atomic

Flat rectangular tabs (n = 270) prepared from spherical (Tytin), admixed (Dispersalloy) or lathe-cut amalgam (ANA 2000) were subjected to aluminum oxide sandblasting with either 50-mu or 90-mu abrasive powder. Mandibular incisor edgewise brackets were bonded to these tabs. An intermediate resin was used, either All-Bond 2 Primers A + B or a 4-META product--Amalgambond Plus (AP) or Reliance Metal Primer (RMP)--followed by Concise. All specimens were stored in water at 37 degrees C for 24 hours and thermocycled 1000 times from 5 degrees C to 55 degrees C and back before tensile bond strength testing. The bond strength of Concise to etched enamel of extracted, caries-free premolars was used as a control. Bond failure sites were classified using a modified adhesive remnant index (ARI) system. Results were expressed as mean bond strength with SD, and as a function relating the probability of bond failure to stress by means of Weibull analysis. Mean tensile bond strength in the experimental groups ranged from 2.9 to 11.0 MPa--significantly weaker than the control sample (16.0 MPa). Bond failure invariably occurred at the amalgam/adhesive interface. The strongest bonds were created to the spherical and lathe-cut amalgams (range 6.8 to 11.0 MPa). Bonds to the spherical amalgam were probably more reliable. The intermediate application of the 4-META resins AP and RMP generally created significantly stronger bonds to all three basic types of amalgam products than the bonds obtained with the All-Bond 2 primers. The effect of abrasive-particle size on bond strength to different amalgam surfaces was not usually significant (p > 0.05). The implications of these findings are discussed in relationship to clinical experience bonding orthodontic attachments to large amalgam restorations in posterior teeth.

Topics: Analysis of Variance; Dental Alloys; Dental Amalgam; Dental Bonding; Dental Stress Analysis; Dentin-Bonding Agents; Materials Testing; Methacrylates; Orthodontic Brackets; Resin Cements; Silver; Statistics, Nonparametric; Surface Properties; Tensile Strength

To evaluate the tensile and shear bond strengths of eight adhesives and two amalgams (spherical and lathe cut).. Two high-copper amalgams (Tytin, spherical; and ANA-2000, dispersed phase) and seven adhesives (Panavia EX, C&B Metabond, Chameleon Metal Resin Cement, All-Bond 2, All-Bond C&B, Photo-Bond and Imperva Dual) were evaluated. An epoxy resin (Stycast 1266) was included as a control for comparison because it was an adhesive material of similar viscosity but different chemistry from the dental adhesives. The aluminum surfaces were sandblasted with 50 microns aluminum oxide just prior to coating with adhesive resins. The testing area was defined with a 4 mm circular adhesive Mylar mask. All adhesives were mixed and handled according to manufacturers' instructions. Freshly mixed amalgam was condensed into the test cavity and onto the surface immediately after coating with adhesive. After 24 hours storage, the bond strengths were determined in an Instron testing machine at a crosshead speed of 2 mm/minute. The debonded surfaces were examined in an optical microscope for site of failure. The few samples which showed failure at the aluminum-resin interface were not included in the study. Selected debonded surfaces were examined by SEM. A 2-way ANOVA (General Levin Models-GLM) was used to analyze the data from both the tensile and shear bond strength tests. GLM was used instead of standard ANOVA because of the unbalanced design. The lack of balance occurred because some of the bonding resin/amalgam groups had different sample numbers.. A wide variation in bond strengths was obtained with adhesive resin cements and not all appeared suitable for adhesive amalgam restorations. Panavia EX, C&B Metabond, Chameleon Metal Resin Cement and All-Bond C&B showed the best potential for amalgam bonding, with shear and tensile bond strengths greater than 8 MPa. Viscous, filled versions of adhesives appeared to be more effective. Choice of amalgam appeared to be less important than choice of adhesive.

Topics: Analysis of Variance; Composite Resins; Dental Alloys; Dental Marginal Adaptation; Dentin-Bonding Agents; Materials Testing; Microscopy, Electron, Scanning; Silver; Tensile Strength

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

This study evaluated the bond strength of four restorative materials to dentin using Amalgambond. Two high-copper amalgams [Tytin; spherical, (T) and Epoque 80; lathe-cute, (E)], a gallium alloy [Gallium Alloy GF (G) and a resin composite [P-50 (P)] were tested. The polished dentin surface was treated with dentin-enamel activator (10 seconds), washed, dried, and adhesive agent was applied (30 seconds). In group A, the dentin adhesive was placed onto the dentin and while still wet, T, E, or G was condensed in cylinders (4 mm diameter) with condensation forces suggested by the manufacturer for a clinical situation. In group B, the cylindrical specimens of restorative material were allowed to set and then adhered to the treated dentin using the adhesive system. For the composite (control), the adhesive was applied to the treated dentin and while still wet, P was layered into the cylinder and cured for a total of 90 seconds. After storage in water (37 degrees C) for 24 hours, all the specimens were tested for tensile bond strength. This study revealed that the bond strength of P was significantly higher than the other materials tested and also that amalgam allowed to set for 1, 6 or 24 hours before adhesion to dentin had a significantly greater bond strength than freshly condensed amalgam. Although the desired high bond strength did not develop in the bonding of the metallic restorative materials, signs of bonding were found.

Topics: Analysis of Variance; Composite Resins; Dental Alloys; Dental Amalgam; Dental Bonding; Dentin; Dentin-Bonding Agents; Gallium; Humans; Materials Testing; Methacrylates; Microscopy, Electron, Scanning; Surface Properties; Tensile Strength; Time Factors

This study assessed the effect of an air-powder abrasive instrument (Prophy Jet) on the surface integrity of a series of restorative materials. Four types of amalgam alloys (Amalcap, Dispersalloy, Tytin, Ana 2000), three types of composite resins (Silux, Brilliant Lux, Adaptic II), a heat-cured resin (SR Vivadent), and porcelain (Vita VMK) fused to a Gr-Ni alloy at 1 mm and 2.5 mm thickness were subjected from 5 mm distance to the abrasive stream at 100 psi for 5 seconds. The resulting surface topography was studied under an electron probe microanalyzer. All of the amalgams presented increased surface roughness and alterations in the surface composition assigned to the destruction of the soluble gamma-2 and n phases. Composite resins showed excessive matrix disruption, exposure of the filler particles and pitting on the prepolymer surfaces. The crown and fixed partial denture resin was the most affected material. Porcelain at 2.5 mm thickness exhibited moderate stain pitting, whereas in 1 mm thickness severe glaze cracking was identified.

Topics: Acrylic Resins; Air; Bisphenol A-Glycidyl Methacrylate; Composite Resins; Copper; Dental Alloys; Dental Amalgam; Dental Porcelain; Dental Prophylaxis; Dental Restoration, Permanent; Electron Probe Microanalysis; Polymethacrylic Acids; Polyurethanes; Powders; Resins, Synthetic; Surface Properties