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Biomedical subjects

J D Adey

Publications and source records attributed to J D Adey.

18 recordsLinked to original sources
PubMed2004

Initial mercury evaporation from experimental Ag-Sn-Cu amalgams containing Pd.

This study examined the Hg evaporation during setting from experimental Ag-Sn-Cu alloy powders with and without Pd. Four series of alloy powders were fabricated to examine the effect on the Hg evaporation of the alloy compositions (all percentages in this report are weight percents): Pd (0-1.5), Cu (9.0-14.0), Ag (57.0-63.7), and Sn (24.9-29.5). These variations in composition produced alloy powders with gamma-Ag3Sn to beta-AgSn ratios varying from 0.0 to 23.9. The total amounts of Hg released from 10 min after trituration were measured from cylindrical specimens (4 x 8mm; n = 4 ) at 37 degrees C using a Hg vapor analyzer. The results were compared to those from commercial alloys (one high-Cu and one low-Cu alloy). All amalgams made from alloys containing 1.5% Pd exhibited lower Hg vapor release than any other amalgams, with the exception of the low-Cu amalgam. The results clearly showed that the alloy formulation affected the mercury evaporation behavior during setting of the resultant amalgams. A small addition of Pd to the alloy can produce amalgams with 50-60% less Hg vapor release during setting than a leading commercial high-Cu amalgam, Tytin.

Copper↗
PubMed1999

Effect of calcium hydroxide and four irrigation regimens on instrumented and uninstrumented canal wall topography.

The topography of instrumented and uninstrumented canal walls exposed to calcium hydroxide and four different irrigation regimens was observed by scanning electron microscopy. After chemomechanical debridement, one tooth in each matched pair was medicated with calcium hydroxide. One week later, the teeth were irrigated and split longitudinally for evaluation. When no calcium hydroxide was used, predentin and pulpal debris covered the dentinal tubules of the uninstrumented surfaces in specimens irrigated with water or EDTA, but was absent on uninstrumented surfaces in specimens irrigated with NaOCl or NaOCl and EDTA. A typical smear layer was absent in instrumented specimens irrigated with NaOCl and EDTA, but covered the dentinal tubules of the instrumented surfaces of the EDTA irrigated specimens (partially) and the water or NaOCl irrigated specimens (completely). Calcospherites or their remnants were seen on the uninstrumented canal walls of specimens irrigated with NaOCl or NaOCl and EDTA, respectively. Calcium hydroxide use did not alter the surface topography in specimens irrigated with water, EDTA, or NaOCl, but seemed to erode the intertubular dentin in specimens irrigated with NaOCl and EDTA. All irrigants seemed to effectively remove most of the calcium hydroxide.

Calcium Hydroxide↗
PubMed1998

Fluoride penetration into the hybrid layer from a dentin adhesive.

PURPOSE: To evaluate the in vitro microleakage of a new fluoride-containing dentin adhesive and to provide evidence for fluoride release from the adhesive and penetration into the dentin. MATERIALS AND METHODS: Class V preparations with margins in enamel and dentin were made in the buccal and lingual surfaces of six extracted human third molars. Six preparations were restored with Scotchbond Multipurpose (SBMP)/Z100 composite and six with a new fluoride containing dentin adhesive (FB)/Litefil composite. After aging for 30 days in water at 37 degrees C, the teeth were stained with silver nitrate, sectioned and graded by two observers for leakage at the enamel and dentin margins. Selected FB specimens were examined in the scanning electron microprobe using WDS for fluoride and EDS for calcium and phosphorous. Fluoride release into water from disks of FB adhesive was evaluated for up to 112 days using a specific ion electrode. RESULTS: Fluoride leached from the adhesive at a decreasing rate with time. The final rate over 112 days was 0.02 ppm/day (0.2 microgram/cm2/day). Leakage at the enamel and dentin margins was similar for both adhesives (Mann-Whitney U-test; P < or = 0.05). SEM evaluation showed the presence of a discontinuous hybrid layer of 2-3 microns. Fluoride was present within, but limited to, the hybrid layer for the FB adhesive. The penetration of fluoride could only be confirmed in areas where leakage had occurred.

Calcium↗
PubMed1995

Mercury vaporization from amalgams with varied alloy compositions.

The fact that mercury is released from dental amalgam restorations after abrasion provides a source of continued controversy over the safe use of this material. Studies have shown that the amount and rate of mercury release vary for different amalgam products. The objective of this study was to determine how alloy composition affects mercury vaporization from experimental amalgams with similar alloy particle size and shape and percent residual mercury. An hypothesis to be tested was that mercury release is dependent upon the concentration of tin in the silver-mercury matrix phase of the amalgam. Seven spherical amalgam alloys (two low-copper and five high-copper) were made by a dental manufacturer (Tokuriki Honten, Japan). Trituration conditions were adjusted so that all set amalgams had the same residual Hg (47.3%). ADA-type amalgam cylinders were aged for 14 days at 37 degrees C, then lightly wet-abraded on #600 silicon carbide, dried, and placed into a tube through which air was blown at a rate of 750 mL/min. Mercury vaporization was monitored with a gold film analyzer (Jerome 411) for 30 min. Total Hg release was determined by integration. We analyzed polished specimens via electron microprobe to determine composition, volume fraction of silver-mercury matrix (gamma 1), and amount of tin in the gamma 1. The results showed a strong negative correlation (r2 = 0.941) between the log of total mercury released and the amount of tin in the gamma 1. The effect of alloy composition, specifically the presence or absence of zinc in the amalgam, could not be definitively determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1994

Hg emission from dental amalgam as related to the amount of Sn in the Ag-Hg (gamma 1) phase.

Previous studies have shown that: (1) different dental amalgams emit different amounts of Hg vapor after surface films have been removed by abrasion (Boyer, 1988); (2) Sn oxide may be the predominant factor in these surface films that inhibit Hg vapor loss (Okabe et al., 1989); and (3) Sn in the Ag-Hg (gamma 1) phase may influence the vapor pressure of gamma 1 (Reynolds, 1974). The purpose of this study was to explore the relationship between Hg vapor emission and the Sn content of the Ag-Hg (gamma 1) phase in dental amalgam. Eleven commercial amalgams were selected whose gamma 1 phases contain different amounts of Sn. Amalgam specimens were ground on 600-grit carborundum paper and immediately placed into an apparatus designed around a gold film Hg vapor detector. Hg vapor loss in air over a 30-minute period was determined, and the log10 Hg loss/volume fraction gamma 1 was plotted vs. the Sn content of the gamma 1 phase for the 11 test amalgams. A linear regression of these data, showing that of the higher the Sn content in gamma 1, the lower the Hg vapor loss, produced a highly significant R2 = 0.94 (p < 0.001). To examine for differences in vapor pressure among alloys, we eliminated the oxidation effect by conducting these same tests in an argon atmosphere. Although the Hg loss was significantly greater in argon than in air, the same differences among alloys were observed. Thus, from the standpoint of both vapor pressure and oxidation, the amount of Sn in the gamma 1 phase of dental amalgam has a significant and specific influence on the potential for Hg vapor emission.

Air Pollution, Indoor↗
PubMed1991

Factors influencing the creep of dental amalgam.

The purpose of this study was to investigate the influence of relevant microstructural and compositional factors on the creep of 12 representative dental amalgams by means of stepwise multiple linear regression. The independent variables accepted by the regression were volume percent of the eta' (Cu6Sn5) phase, grain size of the gamma 1 (Ag2Hg3) phase, volume percent of the gamma (Ag3Sn) plus epsilon (Cu3Sn) phases, number of very small eta' crystals (less than 1.5 microns) per mm, and weight percent of Hg. The results of this regression showed an adjusted R2 of 0.949, significant at p = 0.002.

Copper↗
PubMed1990

Effect of Pd on the clinical performance of amalgam.

The purpose of this study was to determine the effect of a small amount of Pd on the clinical performance of a high-copper spherical-particle dental amalgam. Two identical alloys, with and without 0.5% Pd, were investigated. The marginal fracture, surface texture, and surface luster of 193 clinical restorations were evaluated at one year, those of 182 at two years, and those of 144 at three years of service. In vitro corrosion tests of anodic polarization and constant potential coulometry were also conducted. Over the three-year period, the results showed no differences in marginal fracture or surface texture between the two alloys. However, the alloy with Pd showed a significant superiority in surface luster over this time period. Both corrosion tests showed less electrochemical activity on the part of the alloy containing Pd.

Adolescent↗
PubMed1988

Sn in the Ag-Hg phase of dental amalgam.

In a recent study, Sarkar and Eyer (1986) studied an amalgam which was formed using a unique procedure. Based on their results, they concluded that the solubility of Sn in the Ag-Hg (gamma 1) phase of dental amalgam was virtually nil (less than 0.25 wt%). This finding is contrary to the published results of other investigations. The purpose of the present study was to clarify these disparate findings. A low-copper dental amalgam was examined by electron probe microanalysis. This amalgam was selected because it exhibits unusually large gamma 1 grains (10 microns). Because the influence of the electron-analyzing beam can be completely contained within these large grains, grain boundaries or peripheral phases would not be excited, and a valid analysis of the gamma 1 grains themselves could be made. The analyses showed significant Sn contents of 2.0-3.0 wt%. Analyses of areas which contained grain boundaries showed slight or no differences in Sn content compared with that for the grains alone. Furthermore, secondary electron scans of this dental amalgam failed to reveal the intergranular precipitates of Sn-Hg observed by Sarkar and Eyer (1986) in their amalgam. These different results can be explained by the fact that the unique amalgam investigated by Sarkar and Eyer does not exhibit the same diffusional patterns as does dental amalgam, and that the composition of the gamma 1 in the two amalgams is not the same. The final conclusion is that the Ag-Hg (gamma 1) phase in dental amalgam does indeed contain a significant amount of Sn.

Dental Amalgam↗
PubMed1987

Effect of time at 37 degrees C on the creep and metallurgical characteristics of amalgam.

When aged at 37 degrees C for six months, dental amalgam exhibits a marked decrease in the property of creep. The objective of this study was to investigate the relationship between this decrease in creep and selected metallurgical characteristics. The formation of beta 1 (Ag-Hg), the grain size of gamma 1 (Ag-Hg), and the composition of gamma 1 were chosen for investigation. Creep was determined according to ADA Specification test No. 1, beta 1 was measured by x-ray diffraction, and gamma 1 grain size and gamma 1 composition were determined by electron-probe microanalysis. The results showed that the decrease in creep was related to beta 1 formation and not to changes in either gamma 1 grain size or gamma 1 composition.

Chemical Phenomena↗
PubMed1984

Microprobe analysis of three high-copper amalgams.

Three single-composition, high-copper amalgams were analyzed for the composition of their before- and after-reaction phases. The method used was electron probe microanalysis. The results may be summarized as follows: All alloys consist essentially of Ag3Sn (gamma), Cu3Sn (epsilon), and, in some cases, Ag4Sn (beta). When the original alloy contains higher amounts of Cu, more Cu is found in solution in the Ag3Sn (gamma) and Ag4Sn (beta) phases. The reaction phases in amalgams made from these alloys consist essentially of Ag22Sn Hg27(gamma 1) and Cu6Sn5 (eta'), with no detectable Sn8Hg (gamma 2). When In is present, it is found principally in the Ag3Sn (gamma) and Ag22Sn Hg27(gamma 1) phases, and both the gamma and gamma 1 phases are of different composition than that for the other alloys. When Pd is present, it is found principally in the Cu3Sn (epsilon), Cu6Sn5 (eta'), and Ag22Sn Hg27(gamma 1) phases.

Chemical Phenomena↗
PubMed1979

The influence of final mercury content on the characteristics of a high-copper amalgam.

In this study, specimens of a high-copper amalgam, prepared at different final Hg contents, were examined in several different experiments. The results showed that as the Hg content is increased, a point is reached beyond which creep and the amount of Sn in gamma1 exhibit a sudden increase. As the Hg content is increased further, gamma2 can be detected. These phenomena can be explained by the hypothesis that insufficient Cu is present at higher Hg contents to combine with Sn to form Cu6Sn5.

Chemical Phenomena↗
PubMed1979

Clinical performance of a gold-containing amalgam.

In this study, the clinical performance (marginal fracture) of a gold-containing amalgam was compared to five traditional gamma 2-containing amalgams and one non-gamma 2 amalgam. The results showed that the performance of this gold-containing amalgam was bettered by the non-gamma 2 amalgam and four of the five gamma 2-containing amalgams. A microprobe evaluation of a five-year-old clinical restoration made from this alloy revealed an unusual corrosion pattern.

Chemical Phenomena↗
PubMed1977

Microprobe analysis of a high Cu amalgam alloy.

A new amalgam alloy consisting of spherical particles having a composition of 60% Ag, 27% Sn, and 13% Cu was investigated by microprobe and X-ray diffraction analysis. The alloy seemed to consist of minute dispersion of Cu3Sn, gamma(Ag3Sn), and beta(Ag-Sn). Amalgam made from this alloy exhibited a matrix of gamma1(Ag-Hg) with small reaction phase areas of Cu6Sn5. No gamma2(Sn-Hg) was observed.

Chemical Phenomena↗
PubMed1977

Creep versus microstructure of gamma2-containing amalgams.

An analysis of the relationship between creep and microstructural characteristics of several gamma2-containing amalgams showed the grain size of the Ag-Hg phase (gamma1) to be a predominant factor influencing creep. When gamma1 grain size is increased, creep is reduced.

Chemical Phenomena↗
PubMedDate not supplied

Microprobe analysis of a Au-containing alloy and its amalgam.

Under near-equilibrium conditions, an alloy ingot containing approximately 64% Ag, 26% Sn, and 10% Au was found by X-ray diffraction to consist of large grains demonstrating the gamma (Ag-Sn) structure. Microprobe analysis of these grains showed a 64.2% Ag, 25.3% Sn, and 10.5% Au composition with very small amounts of AuSn2 and AuSn4 segregated at the grain boundaries. When this alloy is manufactured in the form of rapidly colled spherical particles, X-ray diffraction shows both beta (Ag-Sn) and gamma (Ag-Sn) structures with Au substituting for Ag, and microprobe analysis demonstrates a segregation of small high Sn, high Au areas having a AuSn2 composition. When Hg is mixed with these spherical particles, gamma1, some gamma2, and Sn-Au phases (AuSn2 and AuSn4) form. The Au that combines with Sn seems to come from the beta or gamma phases rather than from the Sn-Au segregations in the alloy. The small amount of the gamma2 phase that is initially formed apparently disappears after a short period of time although there is some question as to whether a very small amount may still remain. The Ag-Hg hase (gamma1) is essentially the same as found in conventional amalgams as is the small amount of gamma2 initially formed. Furthermore, a nonequilibrium state seems to be necessary for the early and possibly complete elimination of gamma2. In the as-cast condition, after a period of time at 37 C, A Ag-Hg-Sn phase (beta1) is formed that is similar to that found in conventional amalgams that serve as restorations in the mouth for a period of time. However, in the 135-annealed amalgam, no beta1 appears.

Dental Amalgam↗
PubMedDate not supplied

Quantitative microprobe analysis of amalgam.

A quantitative microprobe analysis was conducted on three commercial amalgams to determine the nature of the phases present. The presence of tin in the Ag-Hg phase (gamma1) was confirmed and Cu-3Sn was found in the original alloy particles. In the dispersant amalgam studied, little Sn-Hg phase (gamma-2) was found and the reaction phase Cu-6Sn-5 was identified.

Copper↗