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PubMed2004

Amalgam studies: disregarding basic principles of mercury toxicity.

Dental amalgam, which has been used for over 150 years in dental practice, consists of about 50% metallic mercury. Studies on animal and humans show that mercury is continuously released from dental amalgam and absorbed by several body tissues. It is widely accepted that the main source of mercury vapor is dental amalgam and it contributes substantially to mercury load in human body tissues. There is still a controversy about the consequences of this additional mercury exposure from amalgam to human health. Many studies were performed to evaluate possible adverse effects. In this comment, these studies were analyzed with regard to their methodical quality by considering the newest findings on mercury toxicity and metabolism. In sum, a number of studies are methodically flawed drawing inaccurate conclusions as to the safety of dental amalgam.

Dental Amalgam↗
PubMed1995

Does amalgam affect the immune system? A controversial issue.

Although in use for more than 150 years, dental amalgam has been questioned more or less vigorously as a dental restoration material due to its alleged health hazard. Humans are exposed to mercury and the other main dental amalgam metals (Ag, Sn, Cu, Zn) via vapour, corrosion products in swallowed saliva, and direct absorption into the blood from the oral cavity. Dental amalgam fillings are the most important source of mercury exposure in the general population. Local, and in some instances, systemic hypersensitivity reactions to dental amalgam metals, especially mercury, occur at a low frequency among amalgam bearers. Experimental and clinical data strongly indicate that these and other subclinical systemic adverse immunological reactions to dental amalgam metals in humans will be linked to certain MHC genotypes, and affect only a small number of the exposed individuals. These individuals will be very difficult to detect in a mixed population of susceptible and resistant individuals, including persons with alleged symptoms due to dental amalgam fillings, where many of the individuals are likely to suffer from conditions with no proven immunological background such as multiple chemical sensitivity syndrome. Intensified studies should be performed to identify such susceptible MHC genotypes, taking advantage of the reported cases of more heavily metal-exposed humans with systemic autoimmune reactions. Further studies will also be needed to ascertain whether the combined exposure to the metals in dental amalgam may lower the threshold for adverse immunological reactions, since recent studies have shown that the metals in alloy, especially silver, may induce autoimmunity in genetically susceptible mice.

Animals↗
PubMed2000

Mercury-induced nummular dermatitis.

We report 2 cases of relapsing nummular dermatitis according to mercury sensitivity, which was confirmed by patch testing. Removal of the amalgam from dental metal alloys markedly improved their skin eruptions. One of the patients, a dentist, experienced exacerbation of the eruptions on his lower legs after handling dental amalgam. Hypersensitivity to haptens such as metals is possibly involved in, at least in some patients, the pathogenesis of nummular dermatitis.

Adult↗
PubMed2004

Cost-effectiveness of removing amalgam from dental wastewater.

Mercury in the form of amalgam is commonly introduced into dental wastewater as a result of amalgam placements and removals. Dental wastewater is primarily discharged to municipal sewers that convey industrial and residential wastewater to publicly owned treatment works (POTWs) for treatment prior to discharge to surface waters. In some localities, the sewage sludge generated by POTWs from the treatment of wastewater is incinerated, resulting in the emission of mercury to the atmosphere. Some of the mercury emitted from the incinerators is deposited locally or regionally and will enter surface waters. An assessment was conducted of the use of mercury in amalgam in California and the discharge of that mercury from dental facilities to surface waters via the effluent from POTWs and air emissions from sewage sludge incinerators (SSIs). The annual use of mercury in amalgam placements conducted in California was estimated to be approximately 2.5 tons. The annual discharge of mercury in the form of amalgam from dental facilities to POTWs as a result of amalgam placements and removals was estimated as approximately one ton. The discharge of mercury to surface waters in California via POTW effluents and SSI emissions was estimated to total approximately 163 pounds. A cost-effectiveness analysis determined that the annual cost to the California dental industry to reduce mercury discharges to surface waters through the use of amalgam separators would range from 130,000 dollars to 280,000 dollars per pound.

California↗
PubMedDate not supplied

[Is amalgam harmful to patients?].

Toxicological data are presented which suggest that amalgam dental fillings containing mercury are a source of minimal but continuous exposure to mercury. However, no documented clinical and epidemiological observations are present as yet which could demonstrate the harmful effect of this exposure.

Dental Amalgam↗
PubMed1993

Clinical evaluation of glass ceramic inlays (Dicor).

The purpose of the study was to evaluate the clinical behavior of ceramic class-II inlays (Dicor) in the first 2 years after placement. As a reference, a similar number of dental amalgam restorations were followed up during the same period. Twenty-five inlays and 25 dental amalgams were placed on premolars and first molars of 20 and 19 patients (15-19 years old), respectively. The inlay preparations were made in accordance with the manufacturer's recommendations, and the inlays were produced by a licensed Dicor laboratory. The inlays were luted, using a glass ionomer cement. The dental amalgam preparations were made using standard class-II preparation techniques and filled with ANA 2000. The inlays were evaluated after 6, 12, and 24 months, and the dental amalgam restorations after 24 months, using the criteria suggested by Ryge. In addition, the 24-month examination included proximal recording of dental plaque and gingivitis. With the exception of two inlays that fractured during the observation period, all ceramic inlays showed excellent ratings for anatomic form, marginal discoloration, and marginal caries at all examinations. Two inlays showed minor marginal defects but were classified within the range of acceptance with no need for replacement. The two fractured inlays were replacements of earlier fractured dental amalgams. The clinical behavior of the dental amalgam restorations was in most respects similar to that of the ceramic inlays. Unlike the inlays, however, no dental amalgams fractured during the observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed2001

Urinary mercury excretion following amalgam filling in children.

OBJECTIVES: Dental amalgam is the major source of inorganic mercury exposure in the general population. Dental amalgam contains approximately 50% mercury, which is a toxic element. Since children are more at risk for mercury toxicity, we aimed to study prospectively the effects of amalgam filling on urinary mercury excretion in 5- to 7-year-old children. METHODS: Children admitted to the Pedodontics Department with no previous amalgam filling, and in a good state of health with one or more carious posterior teeth, were selected. All fillings were placed in one session for each child using Sina (Iran) amalgam powder and Degussa (Germany) mercury, which were mixed by an automated electric amalgamator (Dentomate 3, Germany). Urinary mercury concentrations were estimated before and 9-12 days after amalgam filling by atomic absorption using the mercuric hydride system. RESULTS: Forty-three children (20 male, 23 female) aged 5.95+/-0.92 years and weighing 19.09+/-3.10 kg were studied. Urinary mercury concentrations before and after amalgam filling were 3.83+/-2.45 and 5.14+/-3.14 microg/L, respectively (p = 0.001). There were no statistically significant correlations between the urinary mercury concentrations and any other variables, including the number and surfaces of filled teeth, weight, age, and sex. CONCLUSION: Although there were highly significant increases in urinary mercury concentrations after amalgam filling, no significant correlation was found between the urinary mercury concentration and the amounts of filled amalgam. Additional investigation is required concerning the effects of mercury release from amalgam.

Child↗
PubMed2004

The use of CDA best management practices and amalgam separators to improve the management of dental wastewater.

Concerns over the persistence and effects of mercury in the environment, particularly in wastewater, have increased significantly over the past decade. Because mercury is a component of dental amalgam, comprising about 50 percent of amalgam among other metals, in recent years the concern has affected dental practices and even educational curricula in the dental schools. While numbers vary widely from area to area, on average, it is estimated dentistry contributes less than 1 percent of the mercury generated from human activity to the environment. Despite dentistry's low contribution to the environmental mercury load, organized dentistry's position is that dentistry's role as a public health profession includes environmental stewardship, as well as patient safety, and that dental professionals must act responsibly by taking steps to prevent amalgam waste or any potentially harmful materials from entering the environment, no matter how small the amount. In support of this belief, both the California Dental Association and the American Dental Association have developed recommendations for best practice that dental offices should follow when handling dental amalgam waste. Many dental schools and auxiliary programs have shown their commitment to minimizing detrimental effects to the environment, evidenced by the fact that most, if not all, have incorporated safe work practices including mercury hygiene procedures as part of clinical coursework. Some local jurisdictions hardest hit by the effects of mercury in wastewater have gone even further to recommend, or even require, the installation of amalgam separators in dental offices. This article will describe the history of BMPs and amalgam separators usage in California, and examine the practical aspects of their usage in reducing the discharge of dental amalgam into waste streams.

California↗
PubMed1983

Corrosion of non-gamma 2-amalgams.

Eight different dental amalgams were studied in an in vitro corrosion test. Cylindrical test specimens were stored in weak lactic acid solutions at different pH for 1 month. The concentrations of mercury and copper in the solutions were measured and corrosion depths estimated. The results indicated that more copper was released from non-gamma 2-amalgams compared with conventional ones. The amounts of copper from these amalgams were not directly correlated to the concentration in the alloys. Mercury was released in much lower amounts than copper for all amalgams and seemed to originate from the gamma 1-phase. A low pH promoted the corrosion.

Chemical Phenomena↗
PubMed1981

The effects of cavity smear layer removal on experimental marginal leakage around amalgam restorations.

Unvarnished freshly-packed dental amalgam restorations leak initially. However, with time, a marginal seal is usually effected. It is not known whether the smear layer which forms during cavity preparation is associated with this leakage pattern. This study was undertaken to evaluate experimental marginal leakage around amalgam restorations (left in situ for one and 12 wk) which had been placed in cavities prepared with and without removal of the smear layer in vital and devitalized teeth. The cavities were obturated with two types of dental amalgams, a conventional and a dispersed-phase amalgam. The excised teeth restorations were subjected to a fluorescent dye marginal leakage experiment. All of the short-term specimens leaked severely, but some of the long-term specimens displayed significant sealing properties. No significant differences were found between the two types of amalgams. However, the non-vital tooth specimens and cavities without smear layers displayed significantly improved sealing properties.

Animals↗
PubMed1989

Maximum bond strength of dental luting cement to amalgam alloy.

Although dental amalgam is used frequently under artificial crowns for restoration of severely damaged teeth, there is little information available on the bond between luting cements and this alloy. This study was designed for determination of the strength of the bond between a dental amalgam alloy and three crown-luting cements. Cylinders of dental amalgam were joined in pairs, with use of a zinc-phosphate, a glass-ionomer, and an acrylic-adhesive resin cement. The tensile-fracture stress of 45 samples of each cement was measured with a universal testing machine, and subjected to a Weibull analysis. The fractured surfaces were examined under low magnification with use of a light microscope, and at low and high magnifications with use of a scanning electron microscope, for evaluation of the appearance of the fractured joints. The Weibull analysis demonstrated that the adhesive resin cement provided a stronger and more predictable bond than either the zinc-phosphate or the glass-ionomer cement. The appearance of the fractured surfaces gave no indication of the strength of the joints, a feature that is common to brittle materials. The results suggest that crowns placed on teeth offering a large amalgam-alloy surface could be retained more predictably with an adhesive resin cement.

Acrylic Resins↗
PubMed1990

Effect of placement of amalgam restorations on urinary mercury concentration.

Dental amalgam emits mercury, especially during setting. In addition, the preparation of the amalgam and its compaction into the cavity involve unbound metallic mercury or create a waste product with free metallic mercury. The present study was performed to explore whether emission of mercury in these situations would measurably influence the individual urinary mercury concentration of dental patients as a result of a single-session treatment with dental amalgam restorations. Informed consent was obtained from the patients of nine children about to be treated with amalgam restorations as part of their regular dental care. The children delivered a total of five morning urine samples before, during, and after the treatment period. No effect on the urine mercury concentration was found during the treatment period. Conclusively, one single session of amalgam treatment did not per se represent a mercury exposure of sufficient quantity to be detectable in a longitudinal, individual study.

Adolescent↗
PubMedDate not supplied

Long-term dissolution of mercury from a non-mercury-releasing amalgam.

The hazards of mercury from dental amalgams have long been recognized. This study examined the mercury release from a "non-mercury-releasing" dental amalgam, Composil, over a 104-week period. Four cylindrical specimens were incubated in 10 ml of purified water at 37 degrees C. The incubate was changed at the end of each 24-hour period and assayed for its mercury content at biweekly intervals. Mercury estimation was carried out using cold-vapor, atomic absorption spectrophotometry over a 104-week period. Results showed that the overall mean release of mercury was 43.5 +/- 3.2 micrograms/cm2/24 hr, and the amount of mercury released remained fairly constant during the duration of the experiment. This study showed that Composil releases mercury in quantities that far exceed those detected in other amalgam systems.

Analysis of Variance↗