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PubMed2004

Estimated quantity of mercury in amalgam waste water residue released by dentists into the sewerage system in Ontario, Canada.

AIM: To estimate the quantity of dental amalgam that Ontario dentists release into waste water. METHODS: Information from a self-administered postal survey of Ontario dentists was combined with the results of other experiments on the weight of amalgam restorations and the quantity of amalgam waste that bypasses solids separators in dental offices. Algorithms were developed to compute the quantity of amalgam waste leaving dental offices when dentists used or did not use ISO 11143 amalgam particle separators. RESULTS: A total of 878 (44.0%) of 1,994 sampled dentists responded to the survey. It was estimated that Ontario dentists removed 1,880.32 kg of amalgam (940.16 kg of mercury) during 2002, of which 1,128.19 kg of amalgam (564.10 kg of mercury) would have been released into waste water in Ontario if no dentists had been using a separator. Approximately 22% of the dentists reported using amalgam particle separators. On the basis of current use of amalgam separators, it was estimated that 861.78 kg of amalgam (430.89 kg of mercury or 170.72 mg per dentist daily) was released in 2002. The use of amalgam separators by all dentists could reduce the quantity of amalgam (and mercury) entering waste water to an estimated 12.41 kg (6.21 kg of mercury, or 2.46 mg per dentist per day). CONCLUSION: Amalgam particles separators can dramatically reduce amalgam and mercury loading in waste water released from dental offices.

Algorithms↗
PubMed1977

Practical aspects of quantitative microphotometer system.

The parameters, characteristics and modifications of standard equipment, also operational methods, are discussed in the context of reading errors. The principal errors are identified: photocell and lamp filament temperatures--internally scattered light--sample position and orientation. The application of the instrument to a specific problem (corrosion of dental amalgam) is illustrated.

Dental Amalgam↗
PubMed1998

Mercury as a potential hazard for the dental practitioner.

Mercury has been used for centuries for medical, chemical, metallurgical and electrical applications. It is an element of mystery, which in its metallic form is an enticing silvery liquid that can be as fascinating as it is dangerous. Its use in dental amalgam has a potential for continuous occupational exposure of dental practitioners to mercury vapor. It is imperative that the dental practitioner understands the hazards associated with the use of mercury, and controls exposures to prevent the development of any untoward effects. This article provides an overview of the toxicology of the different forms of mercury to which human exposure occurs and addresses safety issues associated with mercury vapor, the primary form of mercury encountered in the practice of dentistry.

Air Pollutants, Occupational↗
PubMedDate not supplied

The effect of amalgam surface preparation on the shear bond strength between composite and amalgam.

The aim of this study was to investigate the effect of amalgam surface preparation on the short-and long-term in vitro shear bond strength between a dental amalgam (Valiant) and two dental composites (Herculite, Z100) mediated by three universal bonding agents (All-Bond 2, Amalgambond, and Scotchbond Multi-Purpose). Cylinders of dental composite resin were formed on, and bonded to flat amalgam surfaces. Prior to bonding, the amalgam surfaces were: a) ground flat, with the grinding lines oriented parallel to the direction of the shear stress; b) ground flat, with the grinding lines oriented perpendicular to the direction of the shear stress; or c) ground flat and then sandblasted using 50 micrometer Al2O3. A computerized Universal Testing Machine was used to determine the 1-, 7-, and 30-day shear bond strength of 162 samples (six per group) that were stored in distilled water at 37 degrees C. The results, which were statistically analyzed by performing a three-way analysis of variance (ANOVA) and 27 one-way ANOVA followed by modified (Bonferroni) t-tests for between-group comparisons (alpha = 0.05), have shown that: 1) sandblasting resulted in higher shear bond strength than grinding, except for 1-day All-Bond 2, where no differences were identified; 2) there was no difference in the shear bond strength between samples with parallel or perpendicular ground surfaces for a given bonding system and storage time; 3) for All-Bond 2, the 7-day shear bond strength of parallel and perpendicular ground samples dropped to half of the 1-day values, while the sandblasted samples showed a constant, high shear bond strength over 30 days, 4) for Amalgambond, the shear bond strength of parallel, perpendicular, and sand blasted samples was constant over 30 days; and 5) for Scotchbond Multi-Purpose, a sharp drop in the 7-day shear bond strength was recorded for all the samples, irrespective of amalgam surface preparation.

Composite Resins↗
PubMed1992

Amalcore strength recovery following refilling of access preparations with amalgam.

After endodontic treatment through an amalgam core, the recommended procedure is to replace the entire core. This study examined the strength achieved by restoring the access openings with dental amalgam and reported the type of failure during strength testing. Seventy-two Dispersalloy 8 x 8 mm cylindrical specimens were produced using controlled condensation pressures. The specimens were randomized in three groups: (1) controls, (2) 3 mm access preparations wetted with mercury-rich amalgam before restoration, and (3) 3 mm access preparations restored unwetted. The specimens tested for compressive strength were separated in two subsets. The unwetted group demonstrated significantly less strength than the control and wetted group (p less than 0.05), while the unwetted and wetted groups revealed significantly less strength than the control group (p less than 0.05). The mean diametral tensile strength recovery for the wetted and unwetted groups was 76% and 69%, respectively. The qualitative assessment of the fracture zones indicated that wetted specimens exhibited more fractures through the new amalgam core than the unwetted specimens (p less than 0.05). It would appear that amalgam refilling of access preparations through amalgam cores has clinical potential.

Dental Alloys↗
PubMed1976

Microstructure in gold-containing Ag3Sn-amalgam.

The present study was conducted in order to understand the microstructural characteristics in dental amalgam which consists of both spherical and irregular Ag3Sn alloy particles with gold substituted in varying amounts for silver (0, 9, and 15%). Spherical alloy particles were used as obtained from Western Gold and Platinum and irregular alloy particles were prepared in the laboratory and then employed in the present study. The amalgam was prepared from the alloy particles by the trituration and condensation method. The polished and etched samples were studied using the techniques of X-ray diffraction, optical metallography, scanning electron microscopy, and X-ray energy dispersive spectroscopy. The microstructure in both types amalgam studied after two weeks of preparation contains gamma (unreacted Ag3Sn particles), gamma1 (Ag2Hg3), and gamma2 (Sn7-8Hg) phases in pure Ag3Sn-amalgam and gamma, gamma1, and (Au-Sn) phases in gold-containing amalgam. The The (Au-Sn) phase existed in the form of rings surrounding the gamma grains and acted as a barrier for mercury diffusion in Ag3Sn particles.

Dental Amalgam↗
PubMed2003

Lichenoid reactions of murine mucosa associated with amalgam.

BACKGROUND: In 97% of all patients with oral lichenoid reactions (OLR) associated with dental amalgam a removal of the fillings leads to a decline of the lesions, as a minimum. OBJECTIVES: The aim of this study was to determine if contact allergic or local toxic effects or both may contribute to OLR using an animal model with mercury-sensitive and non-sensitive rats. METHODS: Twenty Brown Norway rats, which have a genetic predisposition for an autoimmune syndrome after exposure to mercury and 20 Lewis rats, not mercury sensitive, were treated as follows: 10 animals of each group were sensitized with a low dose of mercuric chloride. Half of all animals received local exposure of the right buccal mucosa to amalgam (left: control), the others to amalgam alloy free of mercury. All rats were patch tested with an amalgam series. RESULTS: After 20 days of exposure 96% of all animals showed white mucosal lesions restricted to the contact zone of the alloy on the treated side, but only up to 25% had a positive patch test reaction to amalgam or inorganic mercury (INM). The lesions showed no relation to species, alloy, sensitization or patch test reaction. CONCLUSIONS: While allergic mechanisms may contribute to mucosal contact lesions in Brown Norway rats, this is less probable in Lewis rats. Mercury in general appears to be irrelevant in the development of ORL in this study. If this holds true for humans as well, patch testing with an amalgam series may be helpful in a minor fraction of all patients with OLR.

Animals↗
PubMedDate not supplied

Mercury exposure due to environmental factors and amalgam restorations in a sample of North Carolina children.

PURPOSE: Dental amalgam restorations provide a potential source for mercury (Hg) exposure in children. This study explored the possibility that Hg levels in dentin of exfoliated primary maxillary canines could detect cumulative Hg exposure from amalgam restorations in a sample of North Carolina children. METHODS: Twenty-seven exfoliated maxillary canines from 3.3 children, without restorations or caries, were assayed for dentin Hg concentration ([Hg]). Urine samples were obtained from 21 subjects and assayed for [Hg] and diet surveys for seafood ingestion were completed for 26 subjects. A surface/month exposure index (SMEI) was compiled from dental records to quantify each child's cumulative exposure to amalgam restorations. RESULTS: Results showed that dentin [Hg] ranged from undetectable levels to 15.7 ppm with a mean of 3.7 ppm. The SMEI scores ranged from 0-638 with a mean of 95. Ten subjects had low SMEI scores of 0-3, nine had scores 4-100, and eight had scores higher than 100. No statistical correlation was found for SMEI scores and dentin [Hg]. Urine Hg levels were found to be negligible and no relationship was found between urine [Hg] and reported ingestion of seafood or SMEI scores. CONCLUSIONS: Hg exposure in this sample of children was low and additional exposure from amalgam restorations could not be detected by the methods used in this study.

Child↗
PubMed1982

Osseous reactions to bimetallic couples composed of amalgam and gold implanted in rat tibias.

Small, bimetallic couples were manufactured by condensing dental amalgam against a gold post which has been placed in polyethylene tubing. These devices were placed in rat tibias and osseous reactions were evaluated microscopically up to 112 days after surgery. The low current levels generated by the bimetallic couples used in this study did not affect the healing rate of the surgical osseous defect. Statistical analysis demonstrated that there were equal amounts of bone deposited at the anodes and cathodes of the experimental implants at all time intervals studied. The small currents produced by experimental implants did not interfere with the normal healing process, and the implications of this study in clinical situations are discussed.

Animals↗
PubMed1997

Mercury levels in plasma and urine after removal of all amalgam restorations: the effect of using rubber dams.

OBJECTIVE: The aim of the present study was to determine whether removal of all amalgam restorations might significantly affect mercury levels in plasma and urine and whether the use of rubber dams might reduce patient exposure to mercury during amalgam removal. METHODS: All amalgam restorations were removed from 18 subjects during a single treatment session in which a rubber dam was used and from 10 subjects when a rubber dam was not used. All amalgam restorations were removed by the same dentist using high-speed cutting, water coolant, and high-volume evacuation. The levels of mercury in plasma and urine were analyzed both before and during the subsequent twelve months after amalgam removal. In order to determine whether removal of all amalgam restorations might cause an exposure large enough to significantly increase the mercury levels in two indicator media for mercury exposure, i.e., plasma and urine, and to determine if the removal might cause a significant decrease in the mercury levels found over time, the one-tailed, paired Students' t-test was used. For each individual, the pre-removal levels were compared with both the levels found in plasma on d 1 and in urine on d 10, and also with the levels found 1 y after removal. Furthermore, in order to examine whether the use of rubber dams had any effect on the mercury levels found after removal, the changes in the mercury levels found were compared between the groups using the Wilcoxon-Mann-Whitney rank sum test. RESULTS: After removal of all amalgam restorations, only the non-rubber dam group showed significant increases in the mercury levels found in plasma (p = 0.012) and urine (p = 0.037). However, one year later, the mercury levels in plasma and urine had sunk significantly below the pre-removal levels for both groups. When the changes in the mercury levels found were compared between the groups, the non-rubber dam group showed a significantly higher increase of mercury in plasma than the rubber dam group the day after removal (p = 0.0010). Compared to the pre-removal mercury levels in plasma and urine, the levels found 1 y after removal of all amalgam restorations were on average 52 +/- 23% (range 4-89%) lower in plasma and 76 +/- 21% (range 20-94%) lower in urine. SIGNIFICANCE: The study showed that dental amalgam had a statistically significant impact on the mercury levels found in plasma and urine in the patients tested, and that the use of a rubber dam during removal of all amalgam restorations significantly reduced the peak of mercury in plasma following removal.

Adult↗
PubMed1995

Slight renal effect of mercury from amalgam fillings.

The current study was to answer the question: Is enough mercury absorbed from dental amalgam fillings to produce renal damage? One hundred healthy adults (18-44 years old) filled out health questionnaires and voided urine samples. Urine mercury concentration and N-acetyl-beta-glucosaminidase (NAG) were measured. Subjects were grouped into those having amalgam fillings (N = 66) and those without (N = 34). Median (95% Confidence Interval) urine mercury was 1 (1-2) and 0 (0-0.6) ng/ml (P < 0.01) and median urine NAG was 23 (18-27) and 16 (11-18) units (P < 0.05) in the two groups respectively. People with mercury amalgam fillings excreted slightly more mercury than people without them, and have a very small increase in urinary NAG excretion that is probably of no clinical significance. This dose of mercury absorbed from amalgam appears to be too little to be a public health hazard for renal injury.

Acetylglucosaminidase↗
PubMedDate not supplied

Dental mercury--a public health hazard.

The aim of this review is to point out the health hazards of the uncontrolled global use of implanted mercury-leaking dental amalgam fillings. In spite of the pandemic use of amalgam, most dentists and doctors are still ignorant about the levels of mercury exposure and its health implications. This review discusses the following chronically neglected aspects in clinical practice: The use of materials science in calculating the mercury exposure levels, which may exceed the TLVs by an order of magnitude; Microbial dissolution and methylation of mercury from amalgam by oral and intestinal bacteria; Diagnostic problems and effects of chronic mercury exposure with emphasis on intestinal, cardiovascular, mental and neurologic symptoms and disorders; Diagnostic value of faeces--instead of urine examination--as the main indicator of Hg exposure; Lack of control groups unexposed to Hg (amalgam free) for epidemiologic investigations of health problems; Contribution of dental mercury to environmental pollution. In conclusion, a lack of interdisciplinary research and of a critical approach to established clinical routine appears to be the reason for the failure of the dental profession to protect the patient from Hg exposure when saving the tooth.

Dental Amalgam↗
PubMed1994

Sensitivity answers sought in amalgam alloy microleakage study.

Sensitivity often occurs shortly after an amalgam restoration is placed. This phenomenon has been related in part to microleakage at the amalgam/tooth interface. When microleakage characteristics of a large number of commercially available dental amalgams were examined, results showed wide variation in the amount of microleakage.

Analysis of Variance↗
PubMedDate not supplied

Quantitative microleakage evaluation around amalgam restorations with different treatments on cavity walls.

The purpose of this in vitro study was to evaluate the dye penetration around amalgam restorations in dentin cavities by a quantitative test. Standardized circular cavities were prepared on the facial surface of 75 extracted human single-rooted teeth, and restored with dental amalgam. Different bonding/sealing treatments were used on the cavity walls before the restorations were placed. The specimens were thermo-cycled between 5 +/- 2 degrees C and 55 +/- 2 degrees C for 500 cycles with 1-minute dwell times, followed by immersion in a 2% methylene blue solution for 12 hours at 37 degrees C. The quantitative microleakage was evaluated by spectrophotometry and was expressed by microgram dye per tooth structure. The results showed that the use of bonded amalgam restorations was more effective in reducing microleakage.

Dental Amalgam↗
PubMed1997

[Amalgam use and mercury emission in the Netherlands].

An overview is presented of the emission of mercury to the environment by restoring teeth with amalgam, extraction, replacement of amalgam, and the final phase of teeth. Important input data were the trade figures of amalgam. The emission of mercury from amalgam fillings are characterized by diffuse spreading. Many small sources are together a substantial source of the leakage of mercury to the environment. Amalgam adhering to cotton-wool and in extracted teeth deliver a relevant contribution to the mercury load in municipal waste. The total mercury emission from dental amalgam to the environment in the Netherlands is at the estimate 500 kg a year, with a worst case maximum of 935 kg.

Dental Amalgam↗
PubMed2006

Evaluating amalgam separators using an international standard.

BACKGROUND: Most amalgam particles generated during placement and removal of amalgam restorations are captured by chair-side traps and suction system traps and filters. Particles not captured can end up in the wastewater discharged from the dental office. Environmental initiatives to reduce the discharge of mercury-containing products such as dental amalgam waste into the environment have sparked interest in the use of amalgam separators. METHODS: The authors used International Organization for Standardization (ISO) Standard 11,143 for Amalgam Separators in a laboratory test to evaluate the amalgam removal efficiency of 13 commercially available amalgam separators and two commercially available filtration devices not marketed as amalgam separators but that have the potential to be used as such. RESULTS: All 13 amalgam separators and the two filtration devices exceeded the ISO Standard 11,143 requirement of 95 percent amalgam removal efficiency. The authors found statistical differences in the efficiency of the separators and filtration devices. No differences were found between the "empty" and "full" conditions for each separator. CONCLUSION AND CLINICAL IMPLICATIONS: This laboratory evaluation shows that amalgam separators and the filtration devices removed at least 97.05 percent of the amalgam in samples with particle-size distribution as specified in ISO Standard 11,143.

Analysis of Variance↗
PubMedDate not supplied

Mercury in saliva and the risk of exceeding limits for sewage in relation to exposure to amalgam fillings.

The concentration of total mercury in stimulated saliva was studied in humans with dental amalgam fillings and in 2 nonamalgam groups. The probability of exceeding the limits of mercury permitted in wastewater increased proportionally as the number of amalgam-filled surfaces increased. The mercury limit for sewage is 0.05 mg/l (= 250 nmol/l) effluent, according to the Council of European Communities directive 84/156/EEC. In neither of the nonamalgam groups was this limit exceeded, but 20.5% in the amalgam group exceeded the limit (p < .001). The risk of exceeding the limit increased 2-fold for every 10 additional amalgam-filled surfaces (odds ratio = 2.0; 95% confidence interval = 1.3, 3.3). These results demonstrate that humans, especially in populated areas, can be a significant source of mercury pollutants. As a consequence of mercury release, bacteria may acquire mercury resistance, as well as resistance to other antimicrobial agents, thus resulting in failure of antibiotic treatment.

Adult↗