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PubMed1979

[Studies on Pd base ternary alloys for dental amalgam. (Part 1) Effect of size and shape of particle on dimensional change and mechanical properties (author's transl)].

Although much efforts have been paid to improve the properties of silver-tin amalgam, some clinical problems are not resolved yet. Palladium alloys have good properties for dental material, and they react on mercury well. So they are considered to be good amalgam alloys. In this paper, palladium base ternary alloys are studied for dental amalgam. The effect of size and shape of particle on dimensional change, compressive strength and hardness is studied. Main results obtained are as follows. (1) The dimensional change of spherical particle amalgam is smaller than that of fine cut particle. The finer the particle size is, the smaller the dimensional change is both for spherical and fine cut particles. (2) The dimensional change of amalgam of 60 wt% Pd-40 wt% Ag alloy decreased by addition of Sn or Cu, and these values under 20 micrometer/cm by addition of more than 5 wt% Cu or 10 wt% Sn. (3) Compressive strength of Pd alloy amalgam scatter so widely that the effects of alloying element are not able to be evaluated. Both maximum compressive strengths are 22 kg/mm2 and 28 kg/mm2 for the alloys containing Cu and Sn respectively. (4) Vicker's hardness of palladium alloy amalgam increased by addition of Sn and ranged 80 approximately 120 for spherical amalgam, which is higher than that of commercial alloy. Significant difference is not found in Cu added alloys. (5) From the analysis by XMA, it is found that matrix is composed of one phase and there is compositional difference between center of matrix and near the particle. Silver is rich in the center of matrix and palladium is rich near the alloy particle. Cu and Sn are seemed to distribute uniformly.

Dental Amalgam↗
PubMed1981

Influence of variation in contact stress on the sliding-wear behaviour of a dental amalgam.

The influence of variation in contact stress on the sliding-water behaviour of a dispersed amalgam has been investigated. The results demonstrate that: (1) the rate of wear of the amalgam in sliding contact with pins fashioned from human enamel remains virtually constant (0.39 +/- 0.06 micrometer/h-1) throughout the range of stresses encountered in vivo; and (2) the wear process involves adhesive transfer of amalgam to the contacting face of the enamel pin during sliding.

Dental Amalgam↗
PubMed2004

Does the wear resistance of packable composite equal that of dental amalgam?

BACKGROUND: There is little evidence that packable composites are sufficiently wear resistant to be used as an alternative to amalgam. PURPOSE: The purpose of this study was to evaluate wear rates of packable composites compared with hybrid resin composites and amalgams by an in vitro wear test. MATERIALS AND METHODS: The following composites were used: three packable composites (SureFil, Dentsply/Caulk, Milford, DE, USA; Alert, Pentron Clinical Technologies, Wallingford, CT, USA; and Solitaire, Heraeus Kulzer, Wehrheim, Germany), two hybrid resin composites (TPH Spectrum, Dentsply/Caulk; and Pyramid enamel, Bisco Inc., Schaumburg, IL, USA), and two amalgams (Tytin, Kerr Manufacturing Co., Romulus, MI, USA; and Dispersalloy, Dentsply/ Caulk). Cylindrical Class I cavities prepared on occlusally flattened, extracted human molars were restored with respective materials according to the manufacturers' instructions. Generalized, localized, and antagonistic enamel wear tests were carried out by a University of Alabama at Birmingham (UAB) wear simulator according to previously reported methods. Seven specimens were tested for each group, and the wear depths were measured on profilometric tracings. The data for each wear mode were independently analyzed by one-way analysis of variance and Fisher's exact test (p < or = .05). RESULTS: The generalized wear values for SureFil (7.0 +/- 3.5 microm), Alert (8.6 +/- 1.8 microm), and Pyramid (3.9 +/- 0.5 microm) were not statistically different from those of amalgam materials (Tytin 5.8 +/- 0.7 microm, Dispersalloy 6.0 +/- 0.9 microm) but were different from those of Solitaire (23.9 +/- 2.6 microm) and TPH (30.6 +/- 5.5 microm). The localized wear values for SureFil (19.8 +/- 14.2 microm) and Alert (28.0 +/- 1.6 microm) were significantly smaller than for all other materials. For antagonistic enamel wear, Solitaire exhibited a minimal value (3.4 +/- 0.9 microm), whereas values of SureFil (12.6 +/- 5.6 microm) and Alert (12.0 +/- 6.6 microm) were not statistically different from those of TPH (11.0 +/- 4.0 microm) and amalgams (Tytin 14.5 +/- 4.3 microm, Dispersalloy 7.8 +/- 3.3 microm). CONCLUSIONS: It can be concluded that SureFil and Alert packable composites possess similar wear resistance and abrasiveness to amalgam on the basis of the limitations of this study, which simulated 3 years of clinical wear.

Acrylic Resins↗
PubMedDate not supplied

Repair strength of dental amalgams.

This study tested the hypothesis that newly triturated amalgam condensed vertically on old amalgam was essential for establishing a bond between the new and old amalgams. Twelve rectangular bars were prepared with Dispersalloy and Tytin to establish their baseline flexure strength values. An additional 12 specimens were made and separated into 24 equal halves. All fracture surfaces were abraded with a flat end fissure bur. Twelve surfaces were paired with the original amalgam, and the remaining 12 surfaces were repaired with a different amalgam. At first, freshly triturated amalgam was condensed vertically on the floor of the specimen mold (Group A). The majority of specimens repaired with Group A failed to establish bond at the repair interface. All repair surfaces were abraded again and prepared by a second method. A metal spacer was used to create a four-wall cavity to facilitate vertical condensation directly on the repair surface (Group B). The specimens were stored in ambient air for seven days prior to flexure testing. The strength of specimens repaired with Group B ranged from 26% to 54% of the baseline specimens. ANOVA showed that amalgams repaired with a different amalgam yielded higher strength values than those repaired with the original amalgam, and the baseline specimens exhibited significantly higher strength values than all the repaired specimens.

Air↗
PubMedDate not supplied

Etches for the microstructure of dental amalgams.

An iodized sodium hydroxide solution is suitable as an etch for conventional amalgams. In diluted form and followed by sodium thiosulfate solution, this may be used on dispersed phase, ternary and quaternary alloy amalgams for clearer results than with the cyanide method. Alternative etches are given for ternary-quaternary materials.

Acid Etching, Dental↗
PubMed1980

Effect of residual mercury content on creep in dental amalgams.

For most of the tested amalgams, the increased mercury content caused by delayed compaction increases the flow or creep. The amalgams that had high creep values when packed early were decidedly affected by the increase in mercury content caused by delay in compaction. Amalgams made with Dispersalloy, Tytin, Sybraloy, and New True Dentalloy are not as sensitive to the mercury content as are some of the others tested. Tests for creep may be related more to clinical practice if they are performed on specimens compacted three minutes after trituration rather than on specimens compacted immediately (a half minute) after trituration. In clinical practice, small amounts of amalgam should be mixed and used immediately after trituration. If the delay between trituration and compaction is longer than three minutes, additional mixes are required. We therefore conclude that, in making a large amalgam restoration, many small mixes have superior results over one large mix.

Chemical Phenomena↗
PubMed1987

Adaptation of eight modern dental amalgams to walls of Class I cavity preparations.

An in vitro study was conducted in which a range of amalgam alloys was condensed into Class I cavity preparations. The force of condensation and increment size were varied to determine the effect of these operator variables on the adaptation, of the alloys investigated, to the prepared cavity walls. Specimens were sectioned, metallographically polished and examined using light and scanning electron microscopes. For each specimen ten random points on the pulpal and both vertical walls were selected to measure the adaptation of the amalgam to the tooth structure. For the Class I cavity preparation the adaptation of all alloys to the vertical walls was better than the adaptation to the pulpal walls. The overall adaptability of the alloy did not appear to be determined by the particle size, shape or composition. Condensation force was the most important factor in influencing adaptation of amalgam to the cavity walls. Heavy condensation forces produced better adaptation for all alloys particularly when condensing small increments.

Dental Alloys↗
PubMed1984

Experimental marginal leakage around dental amalgams placed in artificial cavities.

Experimental marginal leakage of high- and low-Cu amalgam restorations placed in acrylic teeth, where the cavities were untreated or painted with denatured collagen and/or a CaP slurry, was assessed after specimens were stored in a 1% NaCl solution for ten days and for one yr. All specimens stored for ten days showed severe marginal leakage. High- and low-Cu amalgam restorations placed in untreated acrylic teeth cavities formed seals after a storage period of one yr, indicating that these materials are able to form a seal without interacting with a natural tooth cavity interface. Cavities treated with denatured collagen also formed seals in the long-term group. It was apparent that, when the CaP slurry was used, generally more leakage resulted after the year's storage period than when amalgam restorations were placed in uncoated acrylic cavity surfaces or in those painted with denatured collagen.

Acrylic Resins↗
PubMed1990

[Electrochemical examinations to the influence of mechanical treatment of surfaces on the corrosion on different dental amalgams. 2: Measurements of potentiodynamic polarization with high polarization rate].

In a cell with artificial saliva the electrochemical behaviour of amalgam specimens of Germadent, Duragam and ANA 2000 are characterized in dependence of different mechanical treatments of surfaces using cycling voltimetry. In the beginning the influence of roughness on the corrosion is evident, but increasing the influence of chemical composition dominant. Duragam-amalgam is most resistant to corrosion. The content of copper in Duragam has a better effect than the high content of copper in ANA 2000.

Copper↗
PubMedDate not supplied

[Perceived threat related to dental amalgam fillings].

Amalgam carriers without somatic complaints and patients who attribute symptoms to amalgam fillings of their teeth do not differ with respect to toxicologic or allergologic parameters. Somatic complaints of amalgam carriers usually are explained as misattributions of unspecific complaints. Perceived threat is a relevant factor within the theoretical models. For the explanation of health related behavior perceived threat is also an important variable. In the present study perceived threat was a relevant factor for complaints associated with dental material, but not for health related behavior in the sense of caries prophylaxis.

Adult↗