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Purchasing, installing and operating dental amalgam separators: practical issues.

BACKGROUND: Growing environmental concern over the accumulation of mercury in some fish has led some state and local environmental agencies to pursue stricter regulation of mercury in wastewater. Dental offices are an identifiable source of mercury in the form of dental amalgam. Although mercury in dental amalgam is not immediately bioavailable (that is, it has not been shown to contribute significantly to the problem of mercury in fish tissue), environmental agencies in some locales are asking dental offices to install amalgam separators in an effort to reduce amalgam discharges beyond those already achieved through chairside traps and vacuum filters. Field experience indicates that the configuration and operation of the dental office infrastructure can significantly affect the choice of separator, as well as the operation and maintenance of the installed equipment. OVERVIEW: The authors review factors related to office infrastructure and operation that dentists should consider when investing in an amalgam separator. They also provide a cost-analysis worksheet and checklist that may be useful to dentists who are considering purchasing a separator. CONCLUSIONS AND CLINICAL IMPLICATIONS: Before purchasing or installing an amalgam separator, dentists should consider factors specific to the available models, including size and maintenance requirements. In addition, office-specific actors should be considered (such as the plumbing configuration, available space for installation and subsequent access to that space for equipment replacement and maintenance). Dentists also should research whether any local or state regulations exist that might influence product selection or installation. Dentists should consider the effect an amalgam separator could have on existing suction equipment. Finally, dentists will want to consider the short- and long-term costs (including maintenance and parts replacement) of the available options.

Costs and Cost Analysis↗

Dental amalgam and multiple sclerosis: a case-control study in Montreal, Canada.

BACKGROUND: The aetiology of multiple sclerosis (MS) remains poorly understood. Dental amalgams containing mercury have recently been suggested as a possible risk factor for MS. METHODS: In a case-control study conducted between 1991 and 1994, we interviewed a total of 143 MS patients and 128 controls, to obtain information on socio-demographic characteristics and the number of dental amalgams and the time since installation based on dentists' records. RESULTS: Neither the number nor the duration of exposure to amalgams supported an increased risk of MS. After adjustment for age, sex, smoking, and education those who had more than 15 fillings had an odds ratio (OR) of 2.57 (95% CI: 0.78-8.54) compared to those who had none; for individuals whose first amalgam was inserted more than 15 years prior to the study, we found an OR of 1.34 (95% CI: 0.38-4.72). CONCLUSIONS: Although a suggestive elevated risk was found for those individuals with a large number of dental amalgams, and for a long period of time, the difference between cases and controls was not statistically significant.

Adult↗

[The influence of different electrolytes on the electrochemical polarization behaviour of dental amalgams].

The measurements of electrochemical polarization of dental amalgams was studied in 5% sodium chloride aqueous solutions, in an artificial saliva and in natural saliva with different pH-values. The non-gamma-2-amalgams have been reported to have higher corrosion resistance in comparison to gamma-2-phase containing amalgams. The results show that the electrochemical corrosion behaviour is strongly differentiated using natural saliva.

Corrosion↗

Mercury vapor release during insertion and removal of dental amalgam.

During a clinical simulation of insertion and removal of dental amalgams, mercury vapor levels increased slightly, but never exceeded the TLV of 0.05 mg/m3. The addition of indium to dental alloy did not affect the amount of mercury vapor released under these conditions.

Air Pollution, Indoor↗

Urinary mercury levels in females: influence of skin-lightening creams and dental amalgam fillings.

The influence of application of skin-lightening creams and dental amalgam fillings on the urinary mercury (Hg) level was evaluated in 225 females (ages 17 to 58 years) living in Riyadh, capital of Saudi Arabia. The arithmetic mean of the urinary Hg level was 6.96 +/- 20.43 micrograms 1(-1), in the range 0 to 204.8 micrograms 1(-1). The mean urinary Hg level adjusted by creatinine (Cr) was 11.22 +/- 37.23 micrograms g-1 Cr, in the range 0 to 459.37 micrograms g-1. No significant difference in urinary Hg was noted between the females regarding the use of skin-lightening creams. On the other hand, results showed that urinary Hg concentration was influenced by the use and number of dental amalgam fillings. No women were identified with symptoms or signs that could be attributed to Hg intoxication. Urine analyses for creatinine, urea, uric acid, phosphorus, magnesium, glucose and calcium showed significant correlation with urinary Hg. This suggests that chronic exposure to Hg may be associated with a deterioration of renal function.

Adolescent↗

The tensile creep characteristics of dental amalgam. I. Stress dependence.

Equipment is described which enables the determination of the creep behavior of small specimens of dental amalgam under tensile stresses. The apparatus has been used to measure the creep strain of both low and high copper dental amalgams at 34 degrees C, in the stress range 9.4 to 38.8 MNm(-2), for time periods of up to 24 h. Significant differences were found in the controlling creep mechanisms for the various amalgam types. Conventional amalgam displayed classical steady-state creep. The high copper amalgams, however, were best represented by transient creep equations implying interference to the motion of dislocations by the presence of hardening precipitates.

Dental Amalgam↗

Role of fluoride on corrodability of dental amalgams.

The role of fluoride ions on the corrosion behavior of some commercial dental amalgam in artificial saliva solution at pH level 7.1 was studied by using impedance and potentiodynamic polarization techniques. It was found that, the presence of F- ions in an artificial saliva solution at pH 7.1 increases the corrodability of different types of dental amalgam. Sever pitting corrosion occurred at level of 100 mM F- ions. The formulation of amalgam alloys greatly affect the resistance to pitting corrosion; the resistance of the amalgam to pitting follows the order: Dispersalloy >> Phasealloy > Oralloy > Tytin > Valiant-pH.D. It is recommended to avoid oral treatment involving high F- ions concentration in the presence of amalgam restorations.

Corrosion↗

X-ray diffraction and SEM/EDS analyses of phases in new dental amalgams.

The superior clinical performance of several dental amalgams which contain high Cu concentrations and little or no gamma 2 has stimulated the introduction of a number of new amalgam alloys. This investigation sought to study the nature of the phases present in eight commercial systems after trituration. Samples were powdered for X-ray diffraction phase analysis or were polished for SEM/EDS analysis. These methods were complementary since they permitted positive identification of the phases and their distribution and composition, respectively. The matrix phase of all systems was gamma 1 (Ag-Hg). Cu6Sn5 was found as the major Sn-rich amalgamation product. The Cu6Sn5 phase forms reaction zones around th Cu-rich particles with morphological variations from system to system. All amalgams contained the gamma (Ag3Sn) phase, but it was microstructurally distinct only in two particle systems. Small amounts of the gamma 2 (Sn-Hg) phase were found in three systems. These results suggest that there are important microstructural variations in the new Cu-rich systems which could eventually result in variations in clinical performance.

Copper↗

Examination of dietary methylmercury exposure in the Casa Pia Study of the health effects of dental amalgams in children.

This study examined methylmercury concentrations in blood of children participating in the Casa Pia Study of the Health Effects of Dental Amalgams in Children over a 1-yr period and related them to their diets in terms of fish and other seafood consumption. One hundred and fifty children between the ages of 8 and 10 yr who were residents of the Casa Pia School System of Lisbon, Portugal, participated. Parents or caregivers completed a food frequency questionnaire designed specifically for this study at baseline. Children provided urinary and blood samples for mercury determinations at baseline and at 1 yr following placement of dental tooth fillings. Mercury levels in fish samples from children's diets were also obtained. Mercury determinations in urine, blood, and fish were performed using cold vapor atomic fluorescence spectroscopy. The mean value of baseline methylmercury concentrations in blood increased as the report of seafood consumption increased, although not statistically significantly. However, blood methylmercury and total mercury concentrations were significantly lower at 1-yr follow-up than at baseline. Sixty-one percent of parents/caregivers reported that their children consumed fish on a weekly basis. The fish offered at a sample of the schools contained low levels of methylmercury (range 13.9-23.6 ng/g). Thus, children participating in the Casa Pia dental amalgam study are exposed to low dietary levels of methylmercury by way of fish consumption, and this finding was reflected in the low mean blood methylmercury concentrations observed. The present findings indicate that dietary methylmercury is not a significant source of mercury exposure and is not likely to confound the association of dental amalgam mercury with potential health effects in the present study.

Child↗

Crack propagation in conventional and high copper dental amalgam as a function of strain rate.

Dental amalgam prepared from high copper and conventional alloys was evaluated for its compressive strength as a function of deformation rate. Results showed that the compressive strength rose to a maximum as deformation rate increased and then began to fall at higher deformation rates. Crack propagation predominated through the gamma 1 phase and around copper containing particles at lower strain rates. Cracks also occurred through copper containing original particles where the stress at fracture was sufficiently high.

Alloys↗

Dental amalgam mercury exposure in rats.

The aim of this study was to measure the distribution of mercury, in tissues of rats exposed to amalgam over a two months period. Possible interaction of mercury with copper and zinc in organs was also evaluated. Rats were either exposed to mercury from 4 dental amalgams, or fed the diet containing powdered amalgam during two months. Mercury was measured in the kidney, liver and brain, copper in kidney and brain and zinc in kidney. The results showed significantly higher concentrations of mercury in the kidneys and the brains of rats in both exposed groups compared to control. Even after two months of exposure to mercury brain mercury concentration in rats with amalgam fillings was 8 times higher than in the control and 2 times higher than in rats exposed to amalgam supplemented diet. The highest mercury concentration in the latter group was found in the kidneys and it was 5 times higher than in the control group. We found no significant differences between mercury levels in exposed and control rat's liver. Exposure to mercury from dental amalgams did not alter the concentrations of copper and zinc in the tissues. Histopathological analyses of rats tissues did not show any pathological changes. These results support previously proposed nose-brain transport of mercury released from dental amalgam fillings.

Animals↗

Effect of mercury on corrosion of eta' Cu-Sn phase in dental amalgams.

OBJECTIVES: The eta' Cu-Sn phase is the most corrosion-susceptible major component of the microstructure in high-copper dental amalgams, even though metallurgically prepared specimens of the phase are corrosion-resistant. The purpose of this study was to determine if mercury is the cause of the degradation. METHODS: Specimens of metallurgically prepared eta' Cu-Sn phase were tested in synthetic saliva using electrochemical methods. Mercury was adsorbed on the surface by exposure to mercury vapor, and the changes in the corrosion potential and anodic polarization characteristics were determined. Galvanic currents between eta' specimens and a high-copper dental amalgam were measured for both Hg-free and Hg-contaminated eta' electrodes. RESULTS: The Hg-free eta' phase showed a wide region of passivity. Exposure to mercury made the eta' phase electrochemically more active, and current peaks appeared on the polarization curves. The Hg-free eta' electrode was a cathode to a high-copper dental amalgam. The Hg-contaminated eta' electrode started also as a cathode, but became anode after a period of exposure. SIGNIFICANCE: It was concluded that mercury destabilizes the protective passive film on the eta' phase, making the phase more susceptible to corrosion in the oral environment. The results of the galvanic current measurements seem to indicate that the galvanic interaction between eta' and the other phases facilitates the mercury-related degradation.

Chemical Phenomena↗

An application of potentiostatic current--time transients to study the corrosion of dental amalgams.

Potentiostatic current-time transients obtained during anodic polarization of a conventional dental amalgam and its component phases have been analysed to characterize the possible electrochemical reactions involved in amalgam corrosion. These reactions involve such surface phenomena as adsorption, anodic film formation, film dissolution, etc. which are well reflected in current-time transients. The analysis of these transients from the standpoint of thermodynamics, suggests that the saline corrosion of dental amalgam may occur through the dissolution of the passive anodic films on Sn7Hg(gamma2) and Cu6Sn5 (eta') and the dissolution reaction appears to be related to the formation of tin-oxychloride.

Adsorption↗

Neurobehavioral effects from exposure to dental amalgam Hg(o): new distinctions between recent exposure and Hg body burden.

Potential toxicity from exposure to mercury vapor (Hg(o)) from dental amalgam fillings is the subject of current public health debate in many countries. We evaluated potential central nervous system (CNS) toxicity associated with handling Hg-containing amalgam materials among dental personnel with very low levels of Hg(o) exposure (i.e., urinary Hg <4 microg/l), applying a neurobehavioral test battery to evaluate CNS functions in relation to both recent exposure and Hg body burden. New distinctions between subtle preclinical effects on symptoms, mood, motor function, and cognition were found associated with Hg body burden as compared with those associated with recent exposure. The pattern of results, comparable to findings previously reported among subjects with urinary Hg >50 microg/l, presents convincing new evidence of adverse behavioral effects associated with low Hg(o) exposures within the range of that received by the general population.

Affect↗

Creep of dental amalgam as a function of heat treatment.

The creep of dental amalgam was measured as a function of heat treatment of the amalgam. The treatment significantly reduced the creep rate. The beta 1 (Ag-Hg) phase was detected in the heat-treated amalgam by X-ray diffraction and metallographic methods, and it appeared that the reduction in creep rate was due to the gamma 1 leads to beta 1 transformation.

Dental Amalgam↗

The relationship between mercury from dental amalgam and the cardiovascular system.

The findings presented here suggest that mercury poisoning from dental amalgam may play a role in the etiology of cardiovascular disorders. Comparisons between subjects with and without amalgam showed amalgam-bearing subjects had significantly higher blood pressure, lower heart rate, lower hemoglobin, and lower hematocrit. Hemoglobin, hematocrit, and red blood cells were significantly lower when correlated to increased levels of urine mercury. The amalgam subjects had a greater incidence of chest pains, tachycardia, anemia, fatigue, tiring easily, and being tired in the morning. The data suggest that inorganic mercury poisoning from dental amalgam does affect the cardiovascular system.

Blood Pressure↗

Psychological and medical effects of mercury intake from dental amalgam. A status report for the American Journal of Dentistry.

Studies examining health consequences of the release of mercury from dental amalgams have concluded that there is insufficient mercury released from these restorations to cause a medical problem. Although the mercury vapor generated during removal of amalgams will cause a transient increase in the patient's mercury level in tissue fluids, biochemical assays have demonstrated that the increase is too small to have a negative influence on organ systems. This is true even when patients have all their amalgams removed in a single session. Nevertheless, over the past decade, the release of mercury from dental amalgam has been frequently blamed for a variety of health complaints. A number of sensationalized media reports regarding the mercury issue have no doubt contributed to the public concern that has been aroused. Consequently, patients may present at the dentist's office, either self-diagnosed or looking for a cause implicating mercury. In actuality, these patients may have symptoms of either medical problems or psychological disorders such as depression or anxiety. Unfortunately, the incorrect diagnosis may not only mislead, but actually place the patient in a dangerous situation. Two well-controlled studies have indicated that (1) 89% of the patients with self-reported "amalgam illness" had psychogenic disorders, whereas only 6% of the matched-pair manifested symptoms of these psychological disorders; and (2) these alleged "amalgam illness" patients had preneurotic reactive/defensive mechanisms that did not allow them to recognize aggressive and threatening situations which the control group would quickly and readily regard as potentially difficult to manage. Other studies involving psychological assessment seem to confirm that dental therapy (removal of amalgams) for people with alleged "amalgam illness" may, at best, provide a "placebo effect".

Air Pollution, Indoor↗

Evaluation of the mercury exposure of dental amalgam patients by the Mercury Triple Test.

AIMS: To establish and analyse reference data for the mercury burden of patients with and without amalgam fillings. METHODS: Atomic absorption spectroscopy was used to quantify Hg concentrations in the scalp hair and urine (before and after application of dimercaptopropane sulphonate), and Hg release from dental amalgams (using a newly developed, amalgam specific chew test), in 2223 subjects. RESULTS: 50th centiles were 1.3 microg Hg/g creatinine in basal urine, 32 microg Hg/g creatinine after DMPS application, 454 ng Hg/g in hair, and 27 microg Hg per g of chewing gum, which corresponds to about 1 micro g Hg released per minute of chewing. Total Hg intake (from ambient air, drinking water, food, and amalgams) of most patients is well below the provisioned tolerable weekly intake (PTWI) defined by the WHO, unless extremely Hg rich food is consumed on a regular basis. However, for patients exceeding the 75th centile in chew tests, total Hg intake exceeds the PTWI by about 50%, even at the low limit of intake from food. In the absence of occupational exposure, significant Hg release from dental amalgams is a necessary but insufficient condition to obtain a high long term body burden. After removal of dental amalgams, chew tests no longer exhibit oral Hg exposure, while basal urine Hg content and DMPS induced excretion display a exponential decrease (half life about 2 months in both cases). CONCLUSIONS: A standardised procedure for evaluation of the magnitude and origin of the Hg burden of individuals has been developed, which, by comparison with the database presented here for the first time, can serve as a diagnostic tool.

Body Burden↗