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. 2023 Apr 28;16(9):3452. doi: 10.3390/ma16093452

Determination and Calculations of Mercury Vapor Concentration and Energy Released from Freshly Condensed Dental Amalgams Having Various Copper Percentages within the Alloy

Ryan Moxon 1, Zhigang Xu 1, Ikenna Chris-Okoro 1, Sheilah Cherono 1, Dhananjay Kumar 1,*
Editor: Javier Gil1
PMCID: PMC10180447  PMID: 37176331

Abstract

Dental amalgam is an alloy consisting of a mixture of fine metallic powder of silver, tin, zinc, copper, and a trace amount of palladium in combination with about fifty percent elemental mercury that forms a matrix phase. Dental amalgams consisting of a high-copper content are the most common types of alloys currently utilized for the restoration of decayed, broken, and fractured posterior human teeth. The present research objective was primarily to improve the material properties by determining and analyzing the amount of mercury vapor released from dental amalgam received from eight different commercial brands. The mechanical hardness of the alloys was found to increase with an increase in copper content in the amalgam. The effect of copper addition on material aging was also studied. During the release of mercury vapor, the corresponding energies associated with the release of mercury vapor from each sample were determined for each successive measurement. The results indicated that increasing the copper content of the amalgam counters the release of mercury vapor from posterior teeth and improves the hardness properties.

Keywords: mercury vapor concentration, γ1-phase, γ2-phase, phase formation, grain boundary structure, properties, ductility, hardness, corrosion resistance, creep, mercury emission

1. Introduction

Dental amalgam material has been utilized by dentists for the restoration of mainly posterior teeth in humans since about 1833, when it was introduced in the United States from England [1]. There are other dental restorative materials than amalgams being used today, but dentists choose to use dental amalgam for posterior teeth restoration due to its higher relative strength and cost-effectiveness compared to composite resin [1,2]. In 2008, the use of dental amalgam was banned in countries such as Norway, Sweden, and Denmark due to concerns regarding mercury vapor toxicity [3]. In the United States, the American Dental Association (ADA) and the Government approved amalgam’s use in dentistry, as major manufacturers are motivated by sheer profit and dental amalgam’s affordability to customers [4]. Dental restorative material has been known to release mercury vapor at very high levels of concentration when triturated and during subsequent condensation as part of cavity preparation in human teeth [3]. The silver in the alloy is responsible for the setting expansion and creates good atomic bonding with tin, enabling an increase in strength and resistance to corrosion within the alloy [4]. More fundamentally, the silver renders the material adapted to high surface shine when polished after placement in the tooth-prepared cavity by the dentist. The tin usually causes setting contraction and gives the alloy its malleability property. Copper improves strength, minimizes corrosion and tarnishing, reduces creep, and improves marginal leakages. Zinc is the scavenger element that reduces oxidation and enables the removal of impurities in the alloy [5,6].

The classification of dental amalgam falls into two categories: (1) low-copper amalgam (about 6% Cu, conventional alloy), and (2) high-copper amalgam (>6% Cu) [6]. Low-copper amalgam has a composition of 55–60 wt. % silver, 20–29 wt. % tin, 6–8 wt. % copper, and <2 wt. % zinc [6]. The chemical formula of the amalgam is given as Ag3Sn (silver–tin γ) + Hg (elemental-mercury) → Ag3Sn (silver–tin γ phase) + Ag2Hg3 (silver–mercury γ1 phase) + Sn8Hg (tin–mercury γ2 phase) [6]. This takes place with a reduction in the size of the particle as the solubility of Sn and Ag in Hg is limited (0.35 and 0.6 wt. %, respectively) [4,7,8,9]. The silver precipitates out initially as Ag-Hg (γ1 phase), followed by tin in the form of the Sn-Hg (γ2 phase). The set amalgam consists of core γ particles surrounded by a matrix of γ1 and γ2 phases [10,11].

In low-copper alloys, the anodic potential of the Sn8Hg (γ2 phase) is greater than that of the Ag2Hg3 (γ1 phase), and this leads to corrosion and resultant distribution of the γ2 phase; thus, forming the reaction products that develop a protective layer of oxide and hydroxide on the outer surface of the amalgam due to aging [12,13]. It has been established conclusively that this founding phenomenon helps in the deceleration of the rate of oxidation. Mercury in the Sn8Hg (γ2 phase) is released either as mercury vapor or as solutes in the saliva. Since the Sn8Hg (γ2 phase) occupies about 15% vol. of the mixed alloy as a continuous or near-continuous structural component, the corrosion loss of this component weakens the matrix and renders it more susceptible to either marginal breakdown or possible failure, including brittleness. Porosity, which usually exists to some extent in most amalgams, accelerates the corrosion of the material [14].

High-copper amalgam has a composition of 40–60 wt. % silver, 12–30 wt. % tin, 8.5–33 wt. % copper, 0.5–9 wt. % indium, and 1–3.5 wt. % zinc, and in some amalgam alloys, it has a trace amount of palladium (0.7 wt. %) [15]. Researchers have suggested that high-copper amalgam must have a minimum of 12 wt. % copper for the elimination of the γ2 phase, which causes an emission of a high concentration of mercury vapor from the alloy [16,17,18,19]. The development of high-copper amalgam by adding silver–copper eutectic particles to traditional silver–tin lathe-cut particles while dispersion hardening the alloy is reported to produce improved physical properties [20]. However, these are not the result of the dispersion hardening, as the silver–copper eutectic particles were big and too spaced out to inhibit dislocation movement. Instead, these improved properties were due to the formation of Cu6Sn5 η-phase [20,21,22]. The great affinity of tin for copper ensures that the γ2-phase is significantly reduced or partially eliminated in addition to generating visible improvements in physical properties such as increased strength, less tarnishing, corrosion resistance, and creep reduction.

Increased levels of weight percent copper present in dental amalgam alloy [23] enable the interdiffusion of copper into the elemental mercury upon trituration, thus initiating a reaction of Sn8Hg (γ2-phase). This γ2-phase is eliminated through the addition of copper to the alloy. Such methods of transformation occurred through changes in the Cu3Sn (ε-phase) [24,25]. The concept of enthalpy and the Gibbs free energy of the reaction and phase product are considered and utilized for the calculation of the energies released at each time interval during mercury vapor measurements. The two main phases that precipitate subsequent to trituration are Ag2Hg3 (γ1-phase) and Sn8Hg (γ2-phase) [24]. Such precipitates initially coexist with the liquid mercury for a short period of time, approximately 10–15 min, and the mixture maintains a plastic consistency, which allows for the placement and shaping of the amalgam during its condensation into the tooth-prepared cavity. The metallic powder is made to be mixed in correct proportion with liquid mercury (consisting of 40–50 wt. %). During trituration, the mercury becomes supersaturated with the metallic atoms, thus leading to nucleation and the growth of the distinct phases which eventually precipitate from the alloy solution [26,27,28].

The alloy particles are manufactured in micro-cut, fine-cut, and coarse-cut particle sizes. The alloy generally develops phases in the form of binary phases, Ag-Sn (γ-phase), Ag-Sn-Cu (ternary phase), and Ag-tin-Cu-Zn (quaternary phase) [29]. The solubility of copper in the Ag3Sn (γ-phase) is only 1 wt. %. Therefore, excess copper forms the copper-rich phase. The amount and type of phase may vary due to the thermal processing, including the Cu3Sn (ε-phase) and the Cu6Sn5 (ζ-phase). High-copper admixed alloy contains a eutectic microstructure of an Ag-rich γ-phase and a copper-rich γ-phase [30]. Zinc is present in the low-copper amalgam powder, and its concentration exceeds the solubility limits of 1.6 wt. % Ag-Sn (β-phase), and 5.9% subsequently forms Cu5Zn8 [31,32].

During the amalgam aging process, changes in the composition and microstructural phases occur. The reaction of mercury and mercury-rich amalgam continues during the setting. High-copper amalgam produces a lesser amount of γ2-phase and transforms into the Cu6Sn5 phase. Amalgams that have been in place for many years usually present some transformation of the Ag2Hg3 (γ1-phase), subsequently resulting in the Ag9Hg11 (β1-phase) [33]. This loss can occur due to three possible mechanisms:

  1. Dissolution of mercury at the amalgam surface.

  2. Evaporation from the exposed surface of the amalgam.

  3. Migration of mercury to the interface of the remaining portion of the unreacted high-copper particles [34].

Two other phase changes generally seem to manifest and are likely to occur during the aging process besides those associated with corrosion, one of which is the reaction of the deleterious Sn8Hg (γ2-phase) phase with unreacted Cu3Sn to form the Cu6Sn eta-phase [24]. Such will occur in the copper alloy if there is any Sn8Hg (γ2-phase). The other likely change is that of the Ag2Hg3 (γ1-phase) into Ag9Hg11 (β1-phase) [24]. This phenomenon has been observed in high-copper alloy surfaces where corrosion occurred. Diffusion of mercury frequently occurred during transformation of the alloy at room temperature during setting process. Diffusion of mercury vapor originates from the Ag2Hg3 γ1-rich mercury phase, which regularly transforms into the Ag9Hg11 β1 phase [34,35,36,37].

This study examines the microstructural changes of the material with advanced aging. Previous research has shown that when the material slowly undergoes oxidation, the mercury vapor levels decrease as a function of time and the oxidative process [37,38]. Such factors control the material properties, such as compressive strength, ductility, hardness, corrosion resistance, creep, and mercury vapor emission [39]. The research objective was primarily to determine and analyze the amount of mercury vapor released from each brand of dental amalgam, having different copper contents, with equal time duration of vapor measurement.

2. Materials and Equipment

Amalgam brands of capsules in spells of 400 mg, 600 mg, and 800 mg were obtained from commercial distribution dental supply companies such as Henry-Schein Dental (Melville, NY, USA; www.henryschein.com), Darby Dental Supply (Jericho, NY, USA; www.darbydental.com), and Patterson Dental Supply. The amalgam capsules obtained from each of the three suppliers are as follows: (1) Dispersalloy (11.8% Cu, regular-set, 2-spills, 600 mg, blue/white color capsule), (2) Permite C/SDI (15.4% Cu, regular set, 2-spills, 600 mg, purple/gray color capsule), (3) Valliant PHD (20% Cu, regular set, 2-spills, 600 mg, blue color capsule), (4) Megalloy EZ (25% Cu, 56% silver, regular set, 2-spills, 600 mg, purple color capsule), (5) Tytin FC/Kerr (26% Cu, regular set, 2-spills, 600 mg, blue/white color capsule), (6) Tytin/Kerr (28% Cu, regular set, 2-spills, 600 mg, white/yellow color capsule), Tytin/Kerr (28% Cu), (7) Contour/Kerr (31% Cu, regular-set, 2-spills, 600 mg, brown/gray color capsule), (8) Sybralloy/Kerr (33% Cu. regular-set, 2-spills, 600 mg, green/gray colored capsule).

In order to measure the concentration of mercury vapor from freshly condensed dental amalgams of various brands and the energy released at each stage of measurement, a Jerome J505 Mercury Vapor Analyzer (Arizona Instrument, Chandler, AZ, USA) was used during the experimental procedure. The Jerome J505 Instrument works on the principle of drawing an inflow of saturated air with particulates via a built-in pump. The air is made to flow over a gold-metallic strip at a warm temperature. Since gold has a high affinity for mercury atoms, the mercury atoms in the saturated air enter the instrument through an orifice by way of a 12-inch plastic tubing attached to the instrument [40].

The standard unit range for the Jerome J505 Mercury Vapor Analyzer is ng/m3 (50 to 500,000), μg/m3 (0.05 to 500), and mg/m3 (0.00005 to 0.50000). The instrument automatically computes statistical parameters such as the variance, standard deviations, and percentage error in the data obtained. Percentage error indicated ±0.05%, each successive measurement demonstrated similarities in results, and each measurement was obtained under normal conditions [40]. In order to understand the phase purity and orientation of the Dispersalloy and Sybralloy, X-ray diffraction analysis was performed using the Bruker D8 (Billerica, MA, USA).

3. Methodology

The research investigated various samples of dental amalgam prepared first by trituration followed by condensation into samples with diameters of 10 mm andthicnkesses of 4 mm. For this research, eight of the most common brands of dental amalgams (having varying powder compositions) were obtained from commercial manufacturers: Dispersalloy—11.8% Cu, Permite C/SDI—15.4% Cu, Valliant PHD—20% Cu, Megalloy EZ—25% Cu, Tytin FC/Kerr—26% Cu, Tytin/Kerr—28% Cu, Contour/Kerr—31% Cu, Sybralloy/Kerr—33% Cu.

Each sample was polished using rough, medium, and smooth-grade Emory polishing paper and was measured under similar environmental conditions and operating speed (temperature between 20–30 °C at 1 atm). These amalgams were distributed in capsules, and inside this capsule was a thin plastic/polymer membrane that separates the metallic powder on one side from the liquid mercury on the other side. Prior to trituration, the amalgam capsule was inserted between the two vibrating prongs of the Zenith dental variable speed amalgamator, which features a torque motor, having the choice of three speed settings: high (4800 rpm), medium (4200 rpm), and low (3600 rpm). The amalgamator was connected to a 120-vold power supply. At the onset of electric power, the amalgam capsule was allowed to vibrate at this high speed for 15 s for the trituration process of mixing.

Prior to initiating measurement, the Mercury Vapor Analyzer was warmed-up for about 10 min, and a test sample reading was obtained in order to verify the accuracy of the measurements. Amalgam capsules were then condensed and prepared in uniform size. The samples were inserted into a Stony Lab 250 mL borosilicate glass (Nesconset, NY, USA). A 12-inch length of plastic tubing with a diameter of 4 mm was attached to the Stony Lab glass, while the other end was attached to the J505 instrument. At the onset of operations, saturated ambient air containing mercury atoms was drawn through a 12-inch plastic tube with a diameter of 4 mm attached to the 250 mL flask. Saturated air samples containing mercury atoms were drawn into the instrument by means of a built-in electrical pump located inside the instrument. The normal flow rate of saturated air is 1 L/min. The sample air then flows through a scrubber filter and directly into the sample cell located inside the instrument; the entrance of the sample cell is controlled by a one-way valve to prevent back-flow.

Six weeks subsequent to sample preparation, the hardness of each sample was measured using the Microvickers Hardness Tester, Model M-400-H1 (Mitutoyo, Kawasaki, Japan).

Thermodynamic calculation methods were applied in determining the energies released from each sample’s stage of concentration measurement (see Equation (1) [29]. All of the measurements were obtained at room temperature during the research experiment (temperature between 20–30 °C at 1 atm).

The study also examined the microstructural changes of the material with advanced aging by analyzing the X-ray diffraction pattern obtained from both the Dispersalloy and the Sybralloy using the D8 Bruker.

4. Results and Discussions

Table 1 below shows the results recorded from the Mercury vapor analyzer. In accordance with the results, and as demonstrated by Figure 1 below, the amalgam samples released a significant amount of mercury vapor. The Dispersalloy (11.8% Cu) released the highest concentration of mercury vapor, while Sybralloy (33% Cu) released the lowest amount of vapor. The vapor release measurement was conducted starting at zero seconds followed by an interval of 20 s up to 2800 s.

Table 1.

Experimental data for mercury vapor concentration (kg/m3) released from eight brands of dental amalgam samples.

Time (s) Disperse Alloy (kg/m3) Permite C/SDI (kg/m3) Valiant PHD (kg/m3) Megalloy EZ (kg/m3) Tytin FC/Kerr (kg/m3) Tytin/Kerr (kg/m3) Contour (kg/m3) Sybralloy (kg/m3)
11.8% Cu 15.4% Cu 20% Cu 25% Cu 26% Cu 28% Cu 31% Cu (33% Cu)
0 846.085 796.8452 788.7453 654.4776 651.6575 615.6716 513.0673 509.6588
20 838.5543 790.5823 784.0675 651.0781 647.4575 612.7408 510.4512 507.6844
40 821.8564 788.5934 781.8564 648.4752 642.8862 608.8856 507.8546 504.8556
60 796.6544 785.6743 779.5686 645.3237 640.5644 602.5639 505.4364 501.5342
80 787.0785 778.5879 774.9676 643.9465 638.5997 598.4522 499.5089 497.8673
100 780.6533 765.8547 764.6354 641.7498 635.7675 595.4965 496.2395 495.9536
120 773.851 753.6457 750.6793 639.4652 632.7673 591.2894 490.2007 491.8945
140 767.3113 749.4512 744.8476 636.3649 629.5088 588.2098 487.9915 489.6577
160 756.4582 745.463 742.9806 632.8451 625.6554 585.7898 485.9067 485.9676
180 748.9329 738.8486 734.5864 631.9463 622.8789 583.8456 484.773 483.7462
200 734.831 730.6582 729.5655 629.4856 619.7769 580.5487 482.9566 481.6766
220 723.0086 720.7678 719.8867 626.8354 617.3744 578.3008 480.6876 478.5653
240 706.5386 703.5541 700.8723 624.0376 614.8842 575.3065 478.1153 475.7674
260 684.1459 679.7895 675.9665 621.2743 612.3428 573.0678 473.5972 473.8665
280 675.8653 673.8823 671.5434 619.8211 610.8452 569.6458 471.3412 471.8604
300 658.6462 654.6008 650.7685 617.3845 608.4768 567.7342 465.8456 469.6997
320 623.0678 621.0804 618.4437 616.3329 606.5646 563.9647 463.698 464.0767
340 595.9563 591.4318 589.4878 585.5875 583.5453 560.7456 461.9438 461.5682
360 590.5342 589.6074 586.9652 583.7677 581.4436 554.7439 457.8348 458.0634
380 586.6308 583.3116 580.5896 577.3458 575.3876 551.8856 453.1195 454.7683
400 577.8899 570.5078 565.5768 561.6455 559.6763 547.4865 451.7344 451.7554
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Figure 1.

Figure 1

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Decrease in the mercury vapor concentrations of dental amalgam samples as a function of time for the first 1000 s.

4.1. Mercury Vapour Concentration

The results from Table 1 show the decrease in mercury vapor released with the passage of time and with the increase in weight percent copper in each sample.

At the starting time (zero seconds) of the mercury vapor measurement of each alloy, the mercury vapor level for the Dispersalloy (11.8% Cu) gave a value of 846 kg/m3 compared to the concentration value of 796 kg/m3 for the Permite C/SDI (15.4% Cu) brand. For the same starting time for the Permite C/SDI (15.4% copper), the mercury released was much lower in value than that of the Dispersalloy amalgam. This is a verification that the amalgam alloy with the lowest percentage of copper will release the greatest concentration of mercury vapor, because the increased amount of copper added to the alloy will suppress the release of mercury vapor. Such evidence of the mercury vapor released from each amalgam alloy can be seen in the plots of Figure 1 and Figure 2, showing the mercury released for each alloy at intervals of 50 s, 200 s, and 350 s.

Figure 2.

Figure 2

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Comparison of the amount of mercury vapor released from eight amalgam samples with different Cu contents (indicated in the figures) as a function of time: (a) Disperse and Permite, (b) Valiant PHD and Megalloy EZ, (c) Tytin FC/Kerr and Tytin/Kerd, and (d) Controur and Sybralloy dental amalgam.

As observed from the plot of Figure 2, both the mercury vapor levels released from the Contour (31% Cu) amalgam and the Sybralloy (33%) amalgam appear to be about the same. Both alloys have approximately the same amount of copper content in their compositions, thus, each alloy releases that amount of mercury vapor in very close proximity. For the high-copper amalgam alloys such as Contour and Sybralloy, the much-increased copper content serves to eliminate the γ2 phase which is responsible for inducing corrosion and tarnishing within the alloy [41,42].

4.2. X-ray Diffraction Analysis

The X-ray diffraction pattern of Dispersalloy (11.8% Cu) and Sybralloy (33% Cu) shows the relative comparison of the Sn8Hg (γ2-phase), of which a greater amount is present in the Dispersalloy plot, as is demonstrated in Figure 1. The major phase in each the Dispersalloy (11.8% Cu) and Sybralloy (33% Cu) brands is the silver–tin (γ-phase), the strongest phase having the tallest peak. The mercury vapor is released during the γ1-phase (Ag2Hg3) and mostly from Sn8Hg (γ2-phase), which is predominant in the low-copper alloy. The Sybralloy (33% Cu) from Figure 1 showed a reduction in the γ2-phase due to the higher weight percent copper in that alloy. Interestingly, 15% vol. of the matrix phase is composed of Sn8Hg (γ2 phase), which is usually a stable phase [32]. This means that the lesser amount of copper enables strong bonding and is brooched in the Cu3Sn ε-phase or Cu6Sn5 η-prime phase [32,33].

The X-ray diffraction image for Dispersalloy as shown in Figure 3 shows a large accumulation of the γ2-phase, and the X-ray diffraction for Sybralloy showed a lesser amount of the γ2- phase, thus indicating a lesser amount of mercury vapor released from Sybralloy than from Dispersalloy and for the other amalgam samples. Previous research has shown that the material slowly undergoes oxidation, and the mercury vapor levels decrease as a function of time and the oxidative process [37]. Such factors control the material properties, such as compressive strength, ductility, hardness, corrosion resistance, creep, and mercury vapor emission [39].

Figure 3.

Figure 3

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XRD pattern for the Dispersalloy (11.8% Cu) and Sybralloy (33% Cu) dental amalgams.

Attempts have been made to reduce the γ2 phase by increasing the copper content in the alloy, effectively above 13% [1]. It is established that the early full strength of the amalgam is achieved within one hour of placement in the prepared tooth cavity [5]. The setting reaction of this alloy is the same as the reaction for the conventional alloy [10]. After the formation of the γ2 phase, there is a reaction between this and the silver–copper component, leading to the formation of the copper–tin phase and γ1 phase [10,18].

The results of the Vickers hardness measurement as shown in Table 2 above for each of the amalgam samples, showed that the hardness of the amalgam increased with the increase in copper content within each of the samples. Such phenomena are, however, independent of time.

Table 2.

Hardness for each amalgam brand with corresponding percent copper in the alloy.

Alloy Percentage Copper Hardness
Disperse Alloy 11.8 64HV200
Permite 15.4 80HV200
Valliant PHD 20 93HV200
Megalloy EZ 25 100HV200
Tytin FC 26 100.8HV200
Tytin/Kerr 28 101.7HV200
Contour 31 112HV200
Sybralloy 33 129HV200
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4.3. Analysis of Energy Released

The energy of formation given off or generated due to the release of mercury vapor can be determined by the following thermodynamic method (Equation (1)):

E=C × HM (1)

where:

  • E = Energy of reaction due to vapor released.

  • C = Recorded concentration of mercury vapor released.

  • H = Energy given off when one atom of mercury is released (32 kilojoules per mole).

  • M = Molecular weight of mercury (200.59 g per mole)

The energies given off from each of the amalgams at each stage of measurement are determined from the calculations as indicated in Equation (1). A decrease in energy is observed with time; therefore, it can be concluded that the energy is proportional to the concentration of mercury vapor released from the amalgam, regardless of the brand. Also, the higher the copper content present in the alloy, the less mercury vapor is released from the amalgam.

In accordance with the results generated from the plots, it is determined that the amalgam brands with higher copper percentages tend to release a lower concentration of mercury vapor within a shorter time interval, accounting for the steeper gradient of higher copper levels within the alloy. The energy of formation is indeed lower for the alloy having the higher copper percentage in the alloy composition.

The results of the experimental data, as listed in Table 1, give the values of the concentrations of mercury vapor as given off by various amalgam alloys. From the Dispersalloy (11.8% copper) brand of dental amalgam to the Sybralloy (33% copper), the measurement of mercury vapor shows a decrease, indicating that vapor release is directly proportional to the copper content of the alloy. Additionally, the mercury vapor decreases with an increase in time and attains a somewhat steady-state value. Such steady-state values will be further achieved due to the oxidation of the alloy with the passage of time.

Both the Contour (31% Cu) and Sybralloy (33% Cu) brands of amalgam demonstrate the lowest energy of formation, which supports the conclusion that the highest copper content in the alloy produces the least concentration of mercury vapor released from the amalgams. This research has proven the desired results of the experiment. As shown, the hardness of the amalgams increases with increasing copper percentage. The corresponding plot is shown in Figure 4, which shows a graphical representation of the phenomena.

Figure 4.

Figure 4

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Increase in the Vickers hardness number as a function of copper percentage in the alloy.

Further investigation regarding the amalgam alloy is required for designing alloys with optimum compositions. In recent years, the American public has become more concerned and ambivalent about the continued mercury vapor release from dental amalgam. Presumably, as more knowledge of this material propagates, there is a high chance that amalgam could become obsolete due to the concerns of the mercury released from such material.

The energy released versus the time plot was tabulated as shown in Figure 5. The energies given off from each of the amalgams were determined from calculations as shown in Equation (1).

Figure 5.

Figure 5

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Energy of formation of alloys containing different amounts of Cu as a function of time.

5. Conclusions

  1. A systematic study has been performed to determine the release of mercury vapor from the eight most common brands of dental amalgam. The release of Hg vapor in order of decreasing amount is found to be as follows: Disperesalloy Brand, Permite C/SDI, Valliant PHD, Megalloy EZ, Tytin FC, Tytin/kerr, Contour, and Sybralloy.

  2. The hardness of the amalgam is inversely proportional to the mercury vapor released from the alloy (i.e., hardness increases with decreasing copper percentage).

  3. X-ray diffraction confirms larger accumulations of γ2-phase subsequent to trituration.

  4. The amount of energy required for the removal of mercury atoms during vapor release decreases with increasing time duration.

  5. A new dental amalgam alloy can be achieved by possibly introducing a new metal to the existing alloy, such as titanium powder.

In brief, this study concludes that the copper content in amalgam is correlated with the amount of Hg vapor released from the alloy. The low-copper amalgam showed higher releases of Hg vapor. In order to manufacture an improved amalgam alloy, either a reduced quantity of mercury or an increased quantity of copper should be considered when designing the alloy composition, along with the introduction of new material if possible. More research and investigations need to be made into the modification of this alloy without significantly affecting its properties.

Acknowledgments

R.M. acknowledges the financial support he received from the NSF-Partnership for Research and Education in Materials (PREM) grant number DMR-2122067 at North Carolina A and T State University.

Author Contributions

Conceptualization, R.M. and D.K.; Methodology, R.M. and Z.X.; Validation, R.M., Z.X., I.C.-O. and S.C.; Investigation, R.M.; Data curation, R.M.; Writing—review & editing, I.C.-O., S.C. and D.K.; Project administration, D.K. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors have no conflict of interest.

Funding Statement

This research was funded by NSF-Partnership for Research and Education in Materials (PREM) grant number DMR-2122067.

Footnotes

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Associated Data

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Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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