Area ratio effects on metal ion release from amalgam in contact with gold

Abstract – The effect of area ratio, chloride concentration and brushing on amalgam in contact with gold was studied by measuring the amounts of elements released in the electrolyte. A type III gold alloy was stored for 4 months in contact with a conventional amalgam, area relations 6/1 and 6/3, in an electrolyte containing 85 mM NaCl with 10 mM phosphate buffer. A specimen with area relation 6/1 was also stored in a 10 mM NaCl solution with 10 mM phosphate buffer. The solutions were renewed each month and analyzed for Cu, Zn, Sn, Hg, and Ag in an atomic absorption spectrophotometer. Cross-sections of the amalgams were studied in a scanning electron microscope. The tendency for Sn and Cu to be released from the amalgam was greater than for the other elements. The Sn-release probably mainly originated from surface corrosion and Cu-release from subsurface corrosion. A stronger galvanic influence enhanced only the release of Cu, and to a less extent Zn. The subsurface corrosion of the amalgam and increasing release of Cu was, in contrast to the other elements, largely dependent on a high chloride concentration in the electrolyte. Light brushing of the specimens had no effect on the amounts of elements released.     

The effect of hydrogen peroxide concentration on metal ion release from dental amalgam

OBJECTIVES: The aim of this study was to investigate the effect of hydrogen peroxide (HP) concentration on metal ion release from dental amalgam. METHODS: Dental amalgam discs (n=25) were prepared by packing amalgam into cylindrical plastic moulds (10 mm diameter and 2 mm height). The discs were divided into five equal groups and each group was immersed in 20 ml of either 0%, 1%, 3%, 10% or 30% HP solution for 24 h at 37 degrees C. Samples were taken for metal ion release determination (Hg, Ag, Sn and Cu) using inductively coupled plasma mass spectrometry (ICP-MS). The surface roughness of each disc was measured before and after bleaching. RESULTS: The differences in concentration of metal ions released after treatment with 0% (control) and each of 1%, 3%, 10% and 30% HP were statistically significant (p<0.05). Metal ion release for the elements (Hg, Ag, Sn and Cu) increased with exposure to increasing concentrations of HP. Surface roughness measurements of the samples before and after treatments with HP solutions were not significantly different (p>0.05). CONCLUSIONS: Exposure to HP bleaching agent was associated with increased metal ion released from dental amalgams compared to treatment with a control solution. Ion release was in proportion to the peroxide concentration tested, with the highest concentration associated with the greatest metal ion release for all elements investigated.     

The effect of carbamide peroxide treatment on metal ion release from dental amalgam.

OBJECTIVES: There is concern that hydrogen peroxide generated by tooth bleaching agents may cause enhanced metal ion release (including mercury) from dental amalgam following contact. The aim of this in vitro study was therefore to investigate the effect of a carbamide peroxide (CP) based tooth bleaching gel on metal ion release from dental amalgam. METHODS: Dental amalgam discs were prepared according to the manufacturers' instructions. These were treated with either a 10% carbamide peroxide (CP) gel or a 0% CP gel for 24h. Discs were carefully wiped with cotton wool before immersion in distilled water (20 ml) for 24h at 37 degrees C. Following immersion, water samples were taken for metal ion release determination (Ag, Cu, Hg and Sn) using inductively coupled plasma mass spectrometry methods. The specimens were further evaluated for surface changes using scanning electron microscopy (SEM) and Talysurf surface roughness measurements. RESULTS: The differences in concentration of metal ions released after treatment with the 10% CP gel and a placebo gel treatment were not statistically significant (p>0.05). For example, mercury release following treatment with the 10% CP gel and the 0% CP gel was found to be 1.17(0.5) and 0.57(0.1)microgcm(-2), respectively. Roughness measurements for samples treated with the 10% CP gel and 0% CP gel were 2.23(0.47) and 1.74(0.16)microm, respectively, again showing no significant difference between groups (p>0.05). SEM images of the amalgam surfaces showed no apparent differences between treatments. SIGNIFICANCE: Treatment with a 10% CP gel did not significantly enhance subsequent metal ion release from dental amalgams compared to a control gel, contradicting previously published studies.     

Disinfectants' effect on mercury release from amalgam

BACKGROUND: Mercury environmental discharge is under increased scrutiny by the U.S. Environmental Protection Agency (EPA). Dental amalgam should be processed properly to prevent an additional environmental burden. Some processing agencies require that submitted amalgam be noninfectious. Investigations have demonstrated that oxidizing disinfectants mobilize mercury from amalgam into solution and add mercury to the environmental burden if it is disposed of improperly. The authors conducted a study to evaluate the effect of representative disinfectants on amalgam mercury release. METHODS: The authors sized a high-copper spherical amalgam alloy to match that typically found in dental unit suction traps. They exposed 20 grams of the alloy to several disinfectant solutions and evaluated the filtered supernatant solution for mercury content. RESULTS: Chlorine disinfectant materials discharged the most mercury ions, followed by bromide, iodophor, peroxide/peracetic acid and phenolic disinfectants. The quaternary ammonium compound did not discharge mercury ions above the detection limit (0.2 parts per billion) into solution. CONCLUSIONS: A quaternary ammonium compound did not mobilize mercury ions into solution when used as a disinfectant agent for amalgam. Chlorine disinfectants mobilized mercury ions the most, followed by bromide, iodophor, peroxide/peracetic acid and phenolic disinfectants. CLINICAL IMPLICATIONS: Dentists are obligated to be good environmental stewards and should follow practices that reduce environmental mercury release. Dental personnel should be aware that oxidizing disinfectants mobilize mercury ions into solution, which will be added to the environment if they are processed improperly. If required by processing, dental personnel should consider the different oxidizing effects of commonly used disinfectants.     

The release of mercury from dental amalgam and potential neurotoxicological effects

OBJECTIVES: The aim of this study was to estimate the amount of mercury released into both air and saliva from fresh and aged, abraded amalgam discs and then investigate neurotoxic effects of inorganic mercury upon sensory neuronal cultures. METHODS: An air-tight chamber was constructed to allow the combined estimation of mercury species released from amalgam pellets. The level released into air and saliva from both freshly packed and aged-abraded amalgam pellets was assessed. Dorsal root ganglia cultures from male CBA mice were exposed to 1 and 10 microM mercuric chloride concentrations. The effects of this were assessed by means of morphology, adhesion, size and immunocytochemistry. RESULTS: The mercury released into air from dry fresh amalgam was low and less than the recommended industrial exposure limit for mercury. However, covering the discs with saliva reduced air-mercury levels by 46-56% and there was a statistically significant difference in the air-mercury levels recorded (p=0.013-0.048). The mercury released into air from dry abraded amalgam was shown to be above the recommended industrial limit. Coating the abraded amalgam discs with saliva reduced the mercury by 66-72% with the levels recorded being significantly lower (p<0.001). The level of total mercury within the saliva was found to be highly variable. Little change was noted in the neuronal cultures treated with 1 microM mercuric chloride. However, the cultures exposed to high level (10 microM) mercuric chloride showed cells that became rounded and clumped together indicating pathological change.CONCLUSIONS: Amalgam placement appears to present minimal mercury exposure risk. To reduce the amount of mercury released into air, however, amalgam should be polished in a moist atmosphere with high volume aspiration. The neurotoxic effect of mercury appears to be related to concentration, as only in the cultures treated with 10 microM mercuric chloride showed striking qualitative and quantitative cellular changes.     

Mercury vapor release from dental amalgam in patients with symptoms allegedly caused by amalgam fillings

The aim of this study was to determine whether a group of patients with symptoms, self-related to their amalgam restorations, experienced an exposure to mercury vapor from their amalgam restorations that reached the range at which subtle symptoms have been reported in the literature. Furthermore, the aim was to determine whether the mercury exposure for these patients was significantly higher than for controls with no reported health complaints. The symptom group consisted of 10 consecutively selected patients from a larger group, referred by their physicians for investigation into any correlation between subjective symptoms and amalgam restorations. The control group consisted of 8 persons with no reported health complaints. The intra-oral release of mercury vapor was measured between 7 :45 a.m. and 9 :00 p.m. at intervals of 30–45 min. following a standardized schedule. The mercury levels in plasma, erythrocytes, and urine were also determined. The calculated daily uptake of inhaled mercury vapor, released from the amalgam restorations, was less than 5% of the daily uptake calculated at the lower concentration range given by the WHO (1991), at which subtle symptoms have been found in particularly sensitive individuals. The symptom group had neither a higher estimated daily uptake of inhaled mercury vapor, nor a higher mercury concentration in blood and urine than the control group. The study provides no scientific support for the belief that the symptoms of the patients examined originated from an enhanced mercury release from their amalgam restorations.     

Fluoride release from a fluoride-containing amalgam in vivo

Six test subjects using a low fluoride diet collected saliva samples each morning for 1 wk to determine the normal fluoride concentration. During the following 8 wk an acrylic plate, containing amalgam "fillings" corresponding to 6 MOD amalgams in premolars, was worn each night. Saliva samples were collected every morning and analyzed with a fluoride-ion electrode. Normal fluoride values ranged from 1.22 microM to 0.57 microM. The first days after insertion of the plates the fluoride concentration ranged from 91.06 microM to 12.26 microM in the subjects. The following 25-30 days there was an exponential decline of the fluoride concentration in saliva with a half-life of 6 to 7 days. The fluoride level was significantly higher (P less than 0.01) than basal levels in all subjects during this period. The following 20-25 days the fluoride level decreased more slowly, approaching the basal level. One subject had a significantly higher fluoride level for all 8 wk. Since the saliva fluoride concentrations registered seem to be sufficient to enhance remineralization, it is concluded that restorations with this material may have a favorable effect not only on secondary caries, but on any initial demineralization in the mouth.     

Fluoride release from a fluoride-containing amalgam in vivo

Six test subjects using a low fluoride diet collected saliva samples each morning for 1 wk to determine the normal fluoride concentration. During the following 8 wk an acrylic plate, containing amalgam “fillings” corresponding to 6 MOD amalgams in premolars, was worn each night. Saliva samples were collected every morning and analyzed with a fluoride-ion electrode. Normal fluoride values ranged from 1.22 μM to 0.57 μM. The first days after insertion of the plates the fluoride concentration ranged from 91.06 μM to 12.26 μM in the subjects. The following 25—30 days there was an exponential decline of the fluoride concentration in saliva with a half-life of 6 to 7 days. The fluoride level was significantly higher (P < 0.01) than basal levels in all subjects during this period. The following 20–25 days the fluoride level decreased more slowly, approaching the basal level. One subject had a significantly higher fluoride level for all 8 wk. Since the saliva fluoride concentrations registered seem to be sufficient to enhance remineralization, it is concluded that restorations with this material may have a favorable effect not only on secondary caries, but on any initial demineralization in the mouth.     

Fluoride release from glass ionomer-lined amalgam restorations

This study evaluated the amount of fluoride released from glass ionomer-lined amalgam restorations. 50 human extracted molars were divided into five groups of 10 teeth each. Group 1: No restorations. Group 2: Class V cavities (2 x 2 x 7 mm) were made on the facial and lingual surfaces and restored with Dispersalloy amalgam. Group 3: Same as Group 2 except 1 mm of Ketac-Bond glass ionomer cement (GIC) was placed on the axial wall before amalgam insertion. Group 4: Same as Group 2 except 1 mm of Chelon-Silver glass ionomer cement (GIC) was placed on the axial wall before amalgam insertion. Group 5: Same as Group 2 except 1 mm of Ketac-Silver GIC was used before amalgam insertion. Before any treatment, all samples were placed in polyethylene vials with 4 ml of deionized water and thermocycled (100x) for baseline fluoride release levels. After restoration, each tooth was placed in a vial with 4 ml of fresh deionized water. At weekly intervals, each tooth was removed from its aqueous medium and transferred to another vial containing 4 ml of deionized water. Fluoride release was measured four times at weekly intervals with an Orion #9609 fluoride-ion electrode. At one week, Ketac-Bond released significantly more fluoride than Ketac-Silver (P less than 0.01) which released significantly more fluoride than Chelon-Silver (P less than 0.01). At four weeks, there was no significant difference in fluoride release between Chelon-Silver and Ketac-Silver, but Ketac-Bond released significantly more fluoride than either of the other materials (P less than 0.01).     

Cracks in gold crowns cemented on amalgam restorations

Twenty-seven gold crowns, removed from patients with problems such as diffuse pain and metallic taste, have been examined. The gold crowns were made of an ordinary casting gold alloy, type III. The crowns were built on amalgam cores or big amalgam fillings. Eight of these crowns had cracks beginning at the cervical margin and propagating occlusally. The crowns were examined in a scanning electron microscope equipped with an energy-dispersive detector. The study showed that the cracks propagated along the grain boundaries within the gold alloy. In the cracks corrosion products usually found on amalgam were identified. The cracks could be due to intercrystalline stress corrosion or overloading.     

The effect of hydrogen peroxide concentration on metal ion release from dental casting alloys

summary  There are concerns that tooth bleaching agents may adversely affect dental materials. The aim of this study was to test the hypothesis that increasing concentrations of hydrogen peroxide (HP) are more effective than water at increasing metal ion release from two typical dental casting alloys during bleaching. Discs ( n  =   28 for each alloy) were prepared by casting and heat treated to simulate a typical porcelain-firing cycle. Discs ( n  =   7) of each alloy were immersed in either 0%, 3%, 10% or 30% (w/v) HP solutions for 24 h at 37 °C. Samples were taken for metal ion release determination using inductively coupled plasma-mass spectrometry and the data analysed using a two-way anova followed by a one-way anova . The surface roughness of each disc was measured using a Talysurf contact profilometer before and after bleaching and the data analysed using a paired t -test. With the exception of gold, the differences in metal ion concentration after treatment with 0% (control) and each of 3%, 10% and 30% HP (w/v) were statistically significant ( P  <   0·05). Metal ion release from the two alloys increased with increasing HP concentrations (over 3000% increase in Ni and 1400% increase in Pd ions were recorded when HP concentration increased from 0% to 30%). Surface roughness values of the samples before and after bleaching were not significantly different ( P  > 0·05) Exposure of the two dental casting alloys to HP solutions increased metal ion release of all the elements except gold.     

Fluoride release from amalgam restorations lined with a silver-reinforced glass ionomer

This study evaluated the amount of fluoride released from amalgam restorations lined with a silver-reinforced glass ionomer. Thirty human extracted molars were divided into three groups of 10 teeth each. Group 1: Class V cavities were made on the facial surfaces and restored with Dispersalloy amalgam. Group 2: Same as Group 1 except 1 mm of GC Lining glass ionomer cement (GIC) was placed on the axial wall before amalgam insertion. Group 3: Same as Group 2 except 1 mm of Miracle Mix silver-reinforced glass ionomer cement (GIC) was placed on the axial wall before amalgam insertion. Before any treatment, all samples were placed in polyethylene vials with 4 ml of deionized water and thermocycled (100x) for baseline fluoride release levels. After restoration, each tooth was replaced in a vial with 4 ml of deionized water. At weekly intervals, each tooth was removed from its aqueous medium and transferred to another vial containing 4 ml of deionized water. Fluoride release was measured four times at weekly intervals with an Orion #9609 fluoride-ion electrode. At 1 and 4 weeks, Miracle Mix released significantly more fluoride than GC Lining (P less than 0.0001).     

Effect of admixed indium on mercury vapor release from dental amalgam

The purpose of this study was to evaluate the effect of admixed indium on the amount of mercury vapor released from dental amalgam. We made amalgam specimens according to ADA Specification Number 1. We added various amounts (0-14% by weight) of indium to the alloy powder. We also tested the commercial amalgams Dispersalloy, Valiant, and Indiloy. Specimens were held at 37 degrees C and 100% humidity. We used a Jerome Mercury Vapor Analyzer (model 411) to measure the mercury vapor released. We analyzed the data by means of ANOVA and Student-Newman-Keuls procedures. Admixed indium significantly decreased the amount of mercury vapor released from dental amalgams; the period of the greatest effect on mercury vapor released was during the setting phase of amalgam; and dental amalgams with greater than or equal to 8% admixed indium released the least amount of mercury vapor.     

Long-term fluoride release from glass ionomer-lined amalgam restorations.

This in vitro study evaluated the amount of fluoride released from glass ionomer-lined amalgam restorations over a period of 1 year. Class V cavities (2 x 2 x 7 mm) were prepared on the facial and lingual surfaces of 50 extracted human molars randomly distributed into 5 groups: Group 1: No restorations; Group 2: Dispersalloy amalgam alone; Group 3: same as Group 2 except 1 mm of Ketac-Silver was placed on the axial wall before amalgam insertion; Group 4: GC Lining/amalgam; and Group 5: Miracle Mix/amalgam. After restoration, each tooth was thermocycled (100x) at 5 degrees C and 55 degrees C with a dwell time of 30 seconds for baseline fluoride release levels. The teeth were placed in a polyethylene vial containing 4 ml of deionized water. At weekly intervals, each tooth was transferred to a fresh vial. Fluoride release was measured with a fluoride ion specific electrode for 10 consecutive weeks and then again at the end of 1 year. Calibration curves for low level measurements were prepared so the readings could be expressed in micrograms/ml F. At 1 year, fluoride released in micrograms/ml was: Group 1: less than 0.08; Group 2: less than 0.08; Group 3: 0.28; Group 4: 0.68; Group 5: 1.12. An ANOVA was used to evaluate the statistical difference between the groups. At the end of 1 year, measurable amounts of fluoride were recorded for all glass ionomer-lined groups with Miracle Mix and GC Lining releasing significantly more fluoride than Ketac-Silver (P less than 0.002).     

Amalgam. III. Mercury release from amalgam restorations

Patients are exposed to mercury during dental treatment. The major source of exposure to mercury is, however the release of mercury both as vapour and as dissolved mercury, from amalgam restorations. With regard to the dissolution in saliva, corrosion of the restorations appears to be of importance. The modern amalgams have a lower corrosion rate than older ones but emit probably more mercury vapour. Different measurement methods show a rather varying amount of mercury release. The amount of mercury in the tracheal air is of more significance than that in the mouth air. It has been stated that from restorations made of old brands of amalgam 73% of the mercury is disappeared, but according to our estimation utmost 2% will disappear from a large restoration of modern brands.     

Mercury release from dental amalgam after treatment with 10% carbamide peroxide in vitro

OBJECTIVES: The effect of 10% carbamide peroxide on mercury release from dental amalgams was assessed in vitro by using a cold-vapor atomic absorption Mercury Analyzer System. STUDY DESIGN: Samples of 4 commercial brands of dental amalgam, Megaloy (Dentsply/Caulk, Milford, Del), Mega+ (CFPM, Aulnaye, France), Nongama 2 (Silmet, Or Yehuda, Israel), and Valiant Ph.D. (Dentsply/Caulk, Milford, Del), were treated for 48 hours with 10% carbamide peroxide and compared with samples treated with phosphate buffer. RESULTS: Amalgam specimens exposed for 48 hours to 10% carbamide peroxide showed significantly higher concentrations of mercury in solution as compared with specimens treated with phosphate buffer (P <.001). Megaloy and Valiant Ph.D. yielded significantly higher mercury concentrations in solution than Mega+ and Nongama 2 (P <.001). Mega+ yielded significantly higher mercury concentrations in solution than Nongama 2 (P <.05). No significant differences were found in mercury concentrations in solution between Megaloy and Valiant Ph.D. CONCLUSIONS: Treatment with 10% carbamide peroxide bleaching agents caused an increase in mercury release from amalgam restorations, possibly increasing exposure of patients to its adverse effects. Amalgam brands differed in the amounts of mercury release after bleaching with carbamide peroxide.     

Tin and copper release related to charge transfer between short-circuited amalgam and gold alloy electrodes

Short-circuited electrodes of dental amalgams and a gold alloy were used in an attempt to study a possible relationship between the quantity of copper and tin ions released into an electrolyte and the charge transferred between the electrodes. It was found that under the experimental conditions used the quantity of tin ions released was related to the charge transferred between the conventional amalgam and the gold alloy. The same tendency was found using a saliva sample which confined and collected the released tin ions into a small volume when the conventional amalgam specimen was short-circuited to the gold alloy specimen in vivo.