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PubMed1999

Qualitative and quantitative determination of dental amalgam restoration volume.

STATEMENT OF PROBLEM: Volume of tooth structure replaced by an existing restoration, as assessed by visual and radiographic examination, is one diagnostic measure used by dental practitioners and dental insurance agencies to determine the relative need to restore a tooth with a full-coverage cast restoration. However, use of these methods has not been validated. PURPOSE: This study compared the volume of a range of dental amalgam restorations placed in typodont teeth, as estimated by dentists, dental students and laypersons, with the actual volume of each restoration. METHODS AND MATERIAL: Sixty subjects (20 dental school faculty, 20 dental students, and 20 clerical staff [laypersons]) participated. After reviewing photographic images of typodont teeth with mesial-occlusal-distal dental amalgam restorations, subjects estimated the volume of each restoration using various restorations on different teeth as a percentage of its tooth's coronal volume. The actual volume of each dental amalgam restoration and that of the coronal portion of the prepared teeth was calculated with a volumetric displacement technique. The single sample 2-sided t test with a.05 level of significance was used to evaluate the null hypothesis (H0 ): The survey participant's estimates of each restoration's percentage volume are the same as the measured volume values versus the alternative hypothesis (H1 ): estimates differed from the measured volume values. One-way analysis of variance was used to determine the significance of any difference between the estimates of the 3 survey test groups. RESULTS: Average volumes reported by all 3 groups were significantly different than the measured volume values (P <.05). Experience and dental training did not significantly affect a participant's ability to evaluate restoration volumes with greater accuracy. Results reported by dentists, dental students, and laypersons were not significantly different (P >.05). CONCLUSIONS: The volume of a restoration is inaccurately assessed by visual and radiographic examination.

Analysis of Variance↗
PubMed1994

The benefits and risks of dental amalgam: current findings reviewed.

In response to recent concern and research findings about dental amalgam, the U.S. Public Health Service conducted a comprehensive scientific review of its benefits and risks. This review would serve as a basis for re-examining federal policy on the use of dental amalgam as a restorative material. This article summarizes the principal findings, conclusions and recommendations from that review.

Cost-Benefit Analysis↗
PubMedDate not supplied

The use of dental amalgam in pediatric dentistry: review of the literature.

Dental amalgam is widely used as a restorative material even though it is not esthetic and there has been extensive anti-amalgam rhetoric. Although other materials have improved greatly, amalgam has the proven safety record and best cost-to-benefit ratio. Clinical evidence indicates that, in the posterior permanent dentition--where esthetics is not a primary concern--the small, minimally prepared, amalgam restoration, with its margins and any caries-susceptible fissures sealed with resin fissure sealant, is the restoration with the best survival. Amalgam also remains the best direct restorative option when larger restorations are required. In the primary dentition, the data indicates that resin-based composite and resin-modified glass-ionomer serve very well.

Child↗
PubMed1981

The effect of dental amalgams on mercury levels in expired air.

The expired air of a group of 48 persons, 40 with and eight without dental amalgam restorations, was analyzed for its mercury content before and after chewing. Expired air samples were collected in polyethylene bags, and a known quantity of each was pumped into the mercury detector for measurement. The results showed that examined subjects with dental amalgams had higher pre-chewing mercury levels in their expired air than those without amalgams. After chewing, these levels were increased an average of 15.6-fold in the former and remained unchanged in the latter group. It was concluded that in situ dental amalgams can increase the level of mercury in expired air.

Dental Amalgam↗
PubMed2001

Canada-wide standards: a pollution prevention program for dental amalgam waste.

Dentistry and society have long recognized the benefits of using silver-based amalgams to restore and maintain the dental health of patients. However, recent studies by health and environment experts have shown that mercury is of great concern when it enters the biosphere as a contaminant. A rational approach to pollution prevention is mandatory. This article explains the relationship between mercury, particularly dental amalgam waste, and the environment and describes a new pollution prevention initiative intended to ensure that the dental community becomes part of the solution to this serious environmental health problem.

Animals↗
PubMed1988

Risk assessment of mercury exposure from dental amalgams.

Much attention is being focused upon the issue of mercury exposure from dental amalgam restorations and the potential for adverse health effects. This controversy has grown beyond the confines of the dental profession itself and is becoming an emotional public health issue. In hope of regaining good health, many dental patients with chronic systemic diseases are considering replacement of their amalgams. Dentists are increasingly being challenged to prove the safety of amalgams. Recently, systematic methods have been established for quantitative evaluation of environmental risks. This study brings together the quantitative methodologies of risk assessment and the knowledge of mercury exposure from dental amalgams to estimate the safety of dental amalgam restorative therapy. Analysis concludes that the margin of safety for mercury toxicity in humans from dental amalgams is approximately 8- to 30-fold. There are many uncertainties involved in this estimate, and further studies are warranted to improve its precision.

Dental Amalgam↗
PubMed1996

[Study on the significance of mercury accumulation in the brain from dental amalgam fillings through direct mouth-nose-brain transport].

The transport of mercury (Hg) from the oro-nasal to the cranial cavity via a direct route was investigated. In 55 deceased persons, Hg concentrations were measured in the olfactory bulb and the trigeminal ganglion, and the number of dental amalgam fillings was assessed. For the purpose of comparison, Hg concentrations were also determined in the occipital lobe cortex, the pituitary gland and the kidney cortex. Quantitative Hg analysis was performed by cold vapor atomic absorption spectroscopy after acid digestion using high pressure microwave treatment. In the olfactory bulb (geom. mean 17.4 micrograms/kg w. w.), the Hg concentration was significantly higher than in the occipital lobe cortex (geom. mean 9.2 micrograms/kg w. w.) (p < 0.0001). No significant difference was found between the Hg concentration in the trigeminal ganglion (geom. mean 12 micrograms/kg w. w.) and the occipital lobe cortex (alpha = 0.005; p = 0.0342). Regression analysis did not reveal a statistically significant correlation between the number of dental amalgam fillings and the Hg content in the olfactory bulb and the trigeminal ganglion, respectively (alpha = 0.01). Therefore, these results do not support the hypothesis of a significant flow o Hg from dental amalgam fillings to the cranial cavity by a direct oro-nasal route. In contrast, a statistically significant correlation exists between the number of dental amalgam fillings and the Hg concentration in the kidney cortex (r2 = 0.317; p < 0.0001), and, to a lesser extent, the Hg concentration in the occipital lobe cortex (r2 = 0.17; p = 0.0016). The highest Hg concentrations (geom. mean 93.1 micrograms/kg w. w.) were detected in the kidney cortex, followed by the pituitary gland (geom. mean 30.0 micrograms/kg w. w.). In this study, Hg concentration in the pituitary gland did not correlate with the number of dental amalgam fillings.

Adolescent↗
PubMed2000

Influence of thermal treatments on Ag Sn Cu powders in order to reduce mercury contents in dental amalgam.

The mercury content of dental amalgams is a controversial subject with regard to the biological properties of these materials. The object of this study is to optimize the thermal treatments performed on an experimental powder in order to obtain a low mercury ratio (41% by weight) while preserving the desirable clinical qualities of the material. Using atomized powder, two types of thermal treatments are performed: A1, to obtain a partially annealed structure and A2, to obtain a complete homogenization. The kinetics of the amalgamation reaction is mainly evaluated by X-ray diffraction to identify the newly formed phases as a function of setting time. Mechanical properties are evaluated according to the ISO norms at 37 degrees C. Metallographical examination of the amalgams shows a Ag-Hg phase which acts as a matrix incorporating the Cu-Sn and Ag-Sn compounds. The setting kinetics of the A1 amalgams is linear and slightly more rapid than that of the A2 amalgam. The mechanical properties of the amalgams are significantly improved regarding the higher mercury content commercial amalgams. A specific thermal treatment permits us to slow down the diffusion of mercury between the different intermetallic compounds into the powder. The final amalgam composition, thus, most approaches the stoechiometric ratio calculated from a quaternary diagram.

Journal Article↗
PubMedDate not supplied

Dental amalgam as one of the risk factors in autoimmune diseases.

BACKGROUND: Experimental and clinical data published recently show that dental amalgam can give rise to undesirable immunological responses in susceptible individuals. In genetically susceptible strains of experimental animals, mercury and silver can induce autoimmune responses. Sera of patients sensitive to mercury were found to have a higher incidence of autoantibodies relative to controls. OBJECTIVE: The aim of this study was to determine possible presence of antinuclear SSB/La autoantibodies after the in vitro stimulation of peripheral blood lymphocytes with HgCl2. METHODS: Lymphocytes were obtained from patients with autoimmune thyroiditis and increased response to mercury in vitro. Mononuclear cells were cultivated for 6 days with 100 microl HgCl2 solution or with pure medium and the levels of antinuclear autoantibodies SSB/La were assayed by a commercial SSB/La ELISA kit. RESULTS: Increased production of SSB/La autoantibodies in the media following stimulation of peripheral blood lymphocytes with HgCl2 was found in all cases. Using the Student's paired test, the results were significant on the p=0.05 significance level. CONCLUSION: Results imply that, in some patients with thyroiditis, mercury from dental amalgam can stimulate the production of antinuclear antibodies. Dental amalgam may be a risk factor in some patients with autoimmune disease.

Antibodies, Antinuclear↗
PubMed1979

In vitro deformation failure analysis of dental amalgams.

The in vitro deformation failure behavior of the conventional and the recent high copper dental amalgams is studied under different strain rates. The conventional silver-tin amalgams exhibited significant slow compressive flow at low strain rates, but failed catastrophically at the higher loading rates. On the other hand, amalgams containing highest copper contents showed no compressive flow and failed catastrophically at all the loading rates. The slow compressive flow in the conventional dental amalgams indicate that dislocations may play an important role in the deformation process of the amalgams at the lower strain rates.

Copper↗
PubMed2001

Multiple sclerosis and dental amalgam: case-control study in Ferrara, Italy.

Dental amalgam fillings containing mercury have been suggested as a possible risk factor for multiple sclerosis (MS). In the context of a wider program of investigation into environmental risk factors and MS, we conducted a case-control comparison to investigate the alleged association between MS, dental caries, and amalgam fillings. We included 132 MS patients with onset during the last 16 years and 423 controls, matched to cases for sex, age and residence. Data were collected by a personal interview conducted by trained doctors. Cases and controls gave informed consent. Although we report a trend toward a higher number of dental fillings in cases than controls, odds ratios for subjects with exposures of different duration and with different numbers of amalgam fillings were not statistically significant. This case-control study failed to demonstrate an association between either the number of dental amalgam fillings or the duration of exposure to mercury amalgam and MS.

Adult↗
PubMed1997

Potential side effects of dental amalgam restorations. (I). An oral and medical investigation.

The aim of this study was to explore a possible association between health status and self-reported adverse effects related to dental amalgam restorations. A group of 50 consecutive patients (index group), referred for complaints self-related to dental amalgam restorations, was compared with a control group of individuals matched by age, sex and postal zip code. The patients underwent an oral, stomatognathic, medical and clinical chemistry examination. Mercury levels were examined in blood, urine and hair. The results revealed that somatic diseases were more common in the index group (38% versus 6%). Symptoms related to cranio-mandibular dysfunction were reported by 74% of the patients in the index group versus 24% in the control group, and were diagnosed in 62% and 36%, respectively. The oral health status and the number of amalgam surfaces were similar in the 2 groups. No positive skin patch test to mercury was found in any of the groups. The estimated mercury intake from fish consumption, occupational exposure, and mercury levels in blood and urine were also similar and far below levels, where negative health effects would be expected. The correlation between the number of amalgam surfaces and mercury levels in plasma and urine (r=0.43) indicated a release of mercury from dental amalgam restorations in both groups. Since the mercury levels were similar among index patients and controls, mercury was not a likely cause of the impaired health reported by the patients.

Adult↗
PubMed1984

Effect of dental amalgam and nickel alloys on T-lymphocytes: preliminary report.

Preliminary data suggest that dental amalgam and dental nickel alloys can adversely affect the quantity of T-lymphocytes. Human T-lymphocytes can recognize specific antigens, execute effector functions, and regulate the type and intensity of virtually all cellular and humoral immune responses. Normal immune function depends on a proper quantity, quality, and ratio of T-lymphocyte helper and suppressor subsets. Further research may determine the frequency and magnitude of T-lymphocyte reduction and alteration by dental materials.

Adult↗
PubMed1986

[Dental amalgams and allergy].

After a short description of the fundamental basis of allergy, particularly in relation to contact allergy, the authors review the 41 published cases of allergy to dental amalgam consisting of 30 female and 11 male patients. 20 of these patients recovered on removal of the dental amalgam. The most frequent symptoms were of the remote cutaneous type (38/41 cases) while local symptoms, particularly gingivitis and stomatitis, occurred in 17 cases. These probably underestimate the true prevalence of the condition for several reported cases have not been published. The authors then go on to describe the sensitizing property of amalgam in relation to the occupational environment and the length of time that the amalgam has been in the mouth. Mercury is the most common sensitizing agent, but other metals, particularly cooper, zinc or silver could also be implicated. The authors attempted to explain the physio-pathological mechanism of sensitization via the cutaneous as well as the oral, digestive and respiratory tracts by describing the chelating properties of metals with cellular or tissue constituents. In the last chapter, the prevention and clinical treatment of sensitization to dental amalgams is described.

Adolescent↗
PubMed1994

Hg emission from dental amalgam as related to the amount of Sn in the Ag-Hg (gamma 1) phase.

Previous studies have shown that: (1) different dental amalgams emit different amounts of Hg vapor after surface films have been removed by abrasion (Boyer, 1988); (2) Sn oxide may be the predominant factor in these surface films that inhibit Hg vapor loss (Okabe et al., 1989); and (3) Sn in the Ag-Hg (gamma 1) phase may influence the vapor pressure of gamma 1 (Reynolds, 1974). The purpose of this study was to explore the relationship between Hg vapor emission and the Sn content of the Ag-Hg (gamma 1) phase in dental amalgam. Eleven commercial amalgams were selected whose gamma 1 phases contain different amounts of Sn. Amalgam specimens were ground on 600-grit carborundum paper and immediately placed into an apparatus designed around a gold film Hg vapor detector. Hg vapor loss in air over a 30-minute period was determined, and the log10 Hg loss/volume fraction gamma 1 was plotted vs. the Sn content of the gamma 1 phase for the 11 test amalgams. A linear regression of these data, showing that of the higher the Sn content in gamma 1, the lower the Hg vapor loss, produced a highly significant R2 = 0.94 (p < 0.001). To examine for differences in vapor pressure among alloys, we eliminated the oxidation effect by conducting these same tests in an argon atmosphere. Although the Hg loss was significantly greater in argon than in air, the same differences among alloys were observed. Thus, from the standpoint of both vapor pressure and oxidation, the amount of Sn in the gamma 1 phase of dental amalgam has a significant and specific influence on the potential for Hg vapor emission.

Air Pollution, Indoor↗