Dental care using silver amalgam

Dental amalgam is the most widely used filling material in dentistry. In our country there are an estimated 40 million amalgam fillings in place. The mercury present in these fillings has caused health concerns over the last 160 years that amalgam has been used in decayed teeth. The fears have always proven to be unjustified and no harmful effects have ever been demonstrated in dental patients. Mercury can be found in several forms. In dentistry, only the metallic form is used, while inorganic and organic compounds are also present in the environment. The metallic form is absorbed in the human body mostly through the lungs. Once mercury reaches toxic levels inside the body, it will interfere with cell metabolism. Most important among the target organs are the brain, the liver and the kidneys. Elimination occur through urine and feces. Mercury is universally found in blood and urine. The concentration depends on absorption by air, water, nutrition, medication (including dental fillings) and occupational hazards. There are four kinds of objectives to dental amalgam: oral galvanism, toxicity, allergenicity and ecological grievances. Disorders from oral galvanism are difficult and delicate to evaluate as the actual currents are very small. Furthermore, no significant difference can be found in current intensity between patients with and without complaints. Finally patients with complaints often present other oral disorders, the treatment of which most often eliminates all complaints that could be attributed to oral galvanism. Toxicity is dose dependent. Industrial safety rules indicate that the amount of mercury absorbed from dental amalgam fillings is far below the safety level. HgB and HgU levels in patients with amalgam fillings are situated well below the acceptable levels. Allergic disorders are observed in patients with amalgam fillings but far less than expected in view of the wide spread use of dental amalgam. The problem of mercury spilling from dental amalgam fillings into the environment will be resolved by strict legislation in the near future. In this context, it can be stated that the use of dental amalgam is safe and justified. Furthermore, it is also advisable as no other material can meet the actual dental needs as efficiently as can dental amalgam.     

Mercury exposure from dental amalgam fillings: absorbed dose and the potential for adverse health effects

This review examines the question of whether adverse health effects are attributable to amalgam-derived mercury. The issue of absorbed dose of mercury from amalgam is addressed first. The use of intra-oral Hg vapor measurements to estimate daily uptake must take into account the differences between the collection volume and flow rate of the measuring instrument and the inspiratory volume and flow rate of air through the mouth during inhalation of a single breath. Failure to account for these differences will result in substantial overestimation of the absorbed dose. Other factors that must be considered when making estimates of Hg uptake from amalgam include the accurate measurement of baseline (unstimulated) mercury release rates and the greater stimulation of Hg release afforded by chewing gum relative to ordinary food. The measured levels of amalgam-derived mercury in brain, blood, and urine are shown to be consistent with low absorbed doses (1-3 micrograms/day). Published relationships between the number of amalgam surfaces and urine levels are used to estimate the number of amalgam surfaces that would be required to produce the 30 micrograms/g creatinine urine mercury level stated by WHO to be associated with the most subtle, pre-clinical effects in the most sensitive individuals. From 450 to 530 amalgam surfaces would be required to produce the 30 micrograms/g creatinine urine mercury level for people without any excessive gum-chewing habits. The potential for adverse health effects and for improvement in health following amalgam removal is also addressed. Finally, the issue of whether any material can ever be completely exonerated of claims of producing adverse health effects is considered.     

Mercury and dental amalgam fillings

During 1993-95 a total of 169 patients (112 women, 57 men) with a wide range of complaints associated with earlier or present amalgam fillings were seen by the "Dental Biomaterials Adverse Reaction Unit" in Norway. Most patients had amalgam fillings; 19 had removed all amalgam, and 14 were in the process of replacing the amalgam fillings with other materials. Predominant symptoms were of a subjective and general nature (96% of the patients). Muscle and joint pain, headache, dizziness and feeling exhausted comprised the most common symptoms. Intra-oral pathology was observed in 48%. There was a correlation between the amount of amalgam ("amalgam score") and urinary mercury. Those without amalgam fillings and significantly lower values (median = 1.6 micrograms mercury/g creatinine) than those with amalgam fillings (medians: with amalgam = 3.5 micrograms/g; with partial removal of amalgam = 2.7 micrograms/g). Overall, in the present group of patients, no statistically significant correlation seemed to exist between the type and number of subjective symptoms or objective findings and the urinary mercury. This would indicate therefore that there is no straightforward association between urinary mercury and symptoms in the present group of patients.     

Mercury release from amalgam into saliva. An in-vitro study

The aim of the study was to investigate mercury release into salivary fluid and to test whether this release is associated with flow rate, buffer capacity or pH of salivary fluid. Salivary fluid was collected from 18 persons (11 with amalgam fillings, 7 without) and the surface area of the fillings was assessed. Mercury loss in unstimulated saliva was 11.6 ng/min for persons with amalgam and 2.1 ng/min for those without. Multiple regression analysis revealed no association between flow rate, buffer capacity or pH of unstimulated salivary fluid and mercury release.     

Risk estimation of mercury intake from different sources

Biological monitoring of mercury (Hg) in blood, urine and hair was performed in volunteers with amalgam fillings, in subjects who consumed fish and in Hg-exposed workers. It was found that both amalgam fillings and the consumption of fish burden the organism with Hg in the same order of magnitude. The Hg concentrations in urine in the occupationally exposed group were higher by a factor of about 100 compared to the group with amalgam fillings. No pathological changes were found in the exposed workers. It seems safe to conclude that no health-related problems from Hg are to be expected from amalgam fillings.     

Amalgam tooth fillings and man's mercury burden

Next to nutrition, amalgam fillings represent the main source for exposure of the general population to mercury. Toxicological considerations focus on the dose of mercury resulting from such exposure. Various approaches to estimate this dose are reviewed. Introducing the dose into the known toxicokinetic model for mercury, tissue and blood and urine concentrations related to mercury release from the fillings can be predicted. These agree well with autopsy and in vivo observations. An assessment of the health hazard for individuals with amalgam fillings shows that the combined mercury intake from food and amalgam does not exceed the acceptable daily intake. In addition, blood and urine mercury concentrations of amalgam bearers are below one tenth of the critical values associated with the onset of early symptoms or of subclinical effects attributable to mercury.     

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.     

Effect of topical timolol on tissue circulation in optic nerve head

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.     

The future of dental amalgam: a review of the literature. Part 5: Mercury in the urine, blood and body organs from amalgam fillings

This is the fifth article in a series of seven on the future of dental amalgam. This covers the studies of mercury distribution to the blood, body organs and the fetus and its excretion in the urine and faeces of humans and experimental animals. It firstly describes the clinical studies comparing the blood and urine mercury levels in patients with and without amalgam fillings and goes on to consider attempts which have been made to calculate tolerable mercury thresholds for the urine. It secondly describes the studies on the body distribution of mercury from amalgam restorations in experimental animals and human cadavers. It finally describes the studies of mercury distribution to the fetus during pregnancy and includes both studies of experimental animals and human clinical studies. The factors affecting the accuracy of these calculations and the relevance of these results is also extensively discussed.     

Psychologic factors in the etiology of amalgam illness

Eleven patients with amalgam illness aged 33-50 years were investigated by psychodynamic methods. Six of them, all women, were dental nurses and hygienists exposed to amalgam/mercury both from their own dental fillings and occupationally. Four men and one woman were exposed only to amalgam/mercury from their own fillings. Assays of mercury in urine samples and in the ambient air during work routines involving the heaviest exposure indicated that the exposure was far below the levels at which even subclinical symptoms could be indicated by psychometric tests. The psychologic investigation indicated that the symptoms of amalgam illness were psychosomatic. All patients had experienced important psychic traumata in close connection with the first appearance of symptoms. It can be concluded from the psychodynamic dialogues that they had not been able to mourn for a loss in an adequate manner and that the body had been forced to symbolize the great pain in their souls.     

The future of dental amalgam: a review of the literature. Part 2: Mercury exposure in dental practice

This is the second article in a series of seven on the future of dental amalgam. It describes the means of exposure to mercury which can occur in dental surgeries from the storage of mercury, preparation and placement of dental amalgam restorations, polishing dental amalgam restorations, the removal of amalgam fillings and the storage of waste amalgam. It also reports on the monitoring of dental practices and studies on the mercury air levels in dental surgeries and blood and urine levels in dentists and their staff. Also, studies which compare these levels with the health and neurobehaviour of dentists and their staff are included. In addition, it discusses post-mortem studies of the mercury levels in body organs in dentists and controls. It then recommends methods for the safe handling of mercury and dental amalgam. Finally, it discusses the issues surrounding the release of mercury into the environment from dental practices and industry.     

Early diagnosis of impaired glomerular and renal tubule function in patients with acromegaly

BACKGROUND: Albuminuria (A), increased urinary excretion of glycosaminoglycans (GAG) and increased activity of N-acetyl-beta-glucosaminidase (NAG) in urine are early markers of glomerular and tubular changes in various pathological conditions at a time when renal functions do not yet display impaired function and when the changes are still reversible. The objective of the presented study was to assess to what extent these early changes may play a part in acromegaly. METHODS AND RESULTS: In a group of 24 acromegalic patients and in 18 healthy controls the authors examined the microalbuminuria (RIA Immunotech Prague), urinary excretion of glycosaminoglycans (spectrophotometrically by the carbazole method) and they assessed the NAG activity in urine (spectrophotometrically). In acromegalic patients before surgical and pharmacological treatment the authors found, as compared with healthy controls, increased urinary excretion of GAG [4.4 (0.9-22.7) g/mol creat. vs. 2.1 (0.8-5.5) g/mol creat, p < or = 0.001], elevated albuminuria [3.6 (0.3-37.4) g/mol creat. vs. 0.5 (0.1-2.2) g/mol creat, p < or = 0.001 and an enhanced NAG activity [1005 (345-2935) U/l vs. 470 (195-1135) U/l, p < or = 0.001]. The parameters of albuminuria and urinary GAG excretion characterize rather glomerular renal function, they correlate mutually (r = 0.64 p < or = 0.001), while the urinary NAG activity, depending on tubular function, does not correlate with them. No correlation of these parameters with the IGI concentration (for A: 0.3, for GAG: -0.04 and for NAG: -0.02 according to Pearson was found. CONCLUSIONS: In hormonally active acromegalic patients without apparent altered renal functions (normal serum creatinine, Albustix negative) the authors detected early changes of glomerular and tubular functions. They found a significant correction between albuminuria and GAG excretion.     

Functional parameters and 99mtechnetium-dimercaptosuccinic acid scan in acute pyelonephritis

The diagnostic value of 99mtechnetium-dimercaptosuccinic acid (DMSA) scintigraphy, ultrasonography and renal functional parameters [urine N-acetyl-beta-D-glucosaminidase (NAG)/creatinine and urine albumin/creatinine quotients] in acute pyelonephritis (APN) were studied in 39 children (28 girls, 11 boys, median age 9 months, range 2 weeks to 9.4 years, 28 patients < 1 year, 11 patients > 1 year) with first-time urinary tract infection. Ultrasonography of the urinary tract was performed on admission and together with DMSA scintigraphy (< 10 days from admission). Urine NAG/creatinine and urine albumin/creatinine quotients were measured daily and after 6-8 weeks. Ultrasonography revealed abnormalities in 12 of 39 (31%) patients [11/32 patients (34%) with positive DMSA scintigraphy], while DMSA uptake defects were present in 32 of 39 (82%) patients [21/28 < 1 year (75%), 11/11 > 1 year (100%), P = 0.08]. Urine NAG/creatinine and urine albumin/creatinine quotients were significantly higher in children < 1 year with APN, as well as in non-renal fever controls, than in older children. However, in both age groups the urine NAG/creatinine and urine albumin/creatinine quotients were significantly higher in APN than in non-renal fever. The urine NAG and albumin excretion decreased rapidly after the initiation of antimicrobial therapy and had normalized at 6-8 weeks. The size and grade of the DMSA uptake defect (DMSA score) did not correlate with duration of disease at admission, maximum C-reactive protein or maximum fever. The urine NAG/creatinine quotient in the children < 1 year showed, however, a significant correlation with the DMSA score (r = 0.58, P < 0.05), while no correlation was found in the older children. We conclude that DMSA scintigraphy is a sensitive method to confirm the clinical diagnosis of APN, although a substantial number of infants appear to have normal scans. Early determination of the urine NAG/creatinine and albumin/ creatinine quotients may further improve the diagnostics in the infant.     

Mercury content in amalgam tattoos of human oral mucosa and its relation to local tissue reactions

Mucosal biopsies from 48 patients with and 9 without amalgam tattoos were analysed with respect to their mercury content, distribution of mercury in the tissue, and histological tissue reactions. The distribution of mercury was assessed by autometallography (AMG), a silver amplification technique. The mercury content was determined by energy dispersive X-ray fluorescence (EDXRF), a multielemental analysis. Mercury was observed in connective tissue where it was confined to fibroblasts and macrophages, in vessel walls and in structures with the histological character of nerve fibres. A correlation was found between the histopathological tissue reaction, the type of mercury deposition, the intensity of the AMG reaction, and the mercury content. Mercury was also found in patients with amalgam dental fillings but without amalgam tattoos.     

Toxicological and neuropsychological findings in patients presenting to an environmental toxicology service

Patients presenting to an environmental toxicology service are frequently convinced that their multiple symptoms are caused by exposure to environmental toxicants. In order to evaluate the patients' hypotheses, 120 consecutive patients referred by health care providers to the environmental toxicology service for various symptoms were included in an open prospective study. The basic diagnostic procedure included an environmental toxicology questionnaire, psychological tests, a 45 minute interview, a physical examination and standard biomonitoring for cadmium, mercury, lead, lindane, hexachlorobenzene, DDT, DDE, DDD, and pentachlorophenol and a salivary test for mercury released from amalgam. Allergic disease was found in 42 patients. Nineteen of the 42 patients also had psychosomatic disorders. An unusually high release of mercury from amalgam fillings in the saliva test was found in six patients. An environmental toxic exposure was demonstrated in 19 patients (4 lead, 8 DDE, 6 mercury--most likely from broken thermometers, 1 neurotoxic alkyl naphtol derivatives). Ten of the 19 patients had psychosomatic disorders and six had medical/neurological disorders. Only two patients had symptoms attributable to environmental exposure alone. Rather classical psychosomatic disorders were diagnosed in 83 patients. Of the 37 patients without identifiable neuropsychological dysfunction, 18 had allergic disorders and 12 had other medical diagnoses. The diagnosis of a toxic environmental exposure should be performed in an integrated diagnostic approach covering environmental toxicology and medicine as well as psychosomatic medicine.     

Renal proximal disfunction based on activity of n-acetyl-beta-d-glucosaminidase in urine of patients with kidney failure

N-acetyl-beta-D-glucosaminidase (NAG) urine activities of 63 patients with stable and unstable chronic renal failure have been investigated. The values of NAG activity obtained from these patients were compared with NAG activity of 33 normal controls. Abnormal NAG values (> 70 nmol/mg of creatinine) were found in 60 (95.2%) patients with chronic renal failure and the median of all values was 327.8 nmol/mg of creatinine. It was 14-fold greater than the median of values for normal controls. There were any significant differences of NAG values between the patients with massive proteinuria (> 1.5 g/24 h), moderate proteinuria and those without 24 hour proteinuria or non-significant proteinuria (respectively 423.5 +/- 286.3 vs 414.4 +/- 334.8 vs 453.0 +/- 451.3 nmol/mg of creatinine). There was no significant difference between the two subgroups of patients with NAG values above and below 280 nmol/mg of creatinine in age, gender, serum urea and uric acid levels. However, the incidence of patients with NAG values higher than 280 nmol/mg of creatinine was statistically significant in unstable course of renal insufficiency and raised serum creatinine levels. It is suggested that the measurement of NAG excretion may be helpful to monitor unstable process in renal failure.     

Fluoxetine in the treatment of borderline personality disorder]

The debate about mercury and dental amalgam has been one of the longest running in dentistry, and shows no signs of abating. This study aimed to investigate perceptions about mercury in dental fillings among a representative sample of the Australian public. A random sub-sample of participants in a national dental telephone interview survey completed a follow-up postal questionnaire which included four items on dental mercury. The postal survey response rate was 85.2%. Concern about mercury in dental fillings was expressed by 37.5%, while 16.2% reported having requested fillings that do not contain mercury. Avoidance of dental care because of concern about mercury in fillings was reported by 5.8%, but only 4.7% reported having had fillings replaced because they contained mercury. The data indicate that there is a substantial degree of concern about mercury and dental amalgam among the Australian public, but that the dental behavioural and treatment-pattern consequences of that concern are infrequent.     

The significance of urinary N-acetyl-beta-D-glucosaminidase for predicting early stage diabetic nephropathy

We studied urinary N-acetyl-beta-D-glucosaminidase (NAG) in the early stage of diabetic nephropathy in 27 non-insulin-dependent diabetes mellitus (NIDDM) patients with a microalbumin level below 20 mg on 24-hour urine sample. Microalbumin and NAG excretion were measured in 24-hour urine samples collected on three separate occasions within seven days of admission. Creatinine clearance was determined simultaneously. There was a significant negative correlation between the creatinine clearance and 24-hour urinary NAG (r = -0.38, p < 0.05). Elevation of urinary NAG may indicate decreased renal function during early stage NIDDM nephropathy.     

Glomerular and tubular function in glycogen storage disease

Urinary protein and calcium excretion were assessed in 77 patients with the hepatic glycogen storage diseases (GSD): 30 with GSD-I (median age 12.4 years, range 3.2-32.9 years), 25 with GSD-III (median age 10.5 years, range 4.2-31.3 years) and 22 with GSD-IX (median age 11.8 years, range 1.2-35.4 years). Inulin (Cinulin) and para-aminohippuric acid (CPAH) clearances were also measured in 33 of these patients. Those with GSD-I had significantly greater albumin (F = 15.07, P < 0.001), retinol-binding protein (RBP) (F = 14.66, P < 0.001), N-acetyl-beta-D-glucosaminidase (NAG) (F = 9.41, P < 0.001) and calcium (F = 7.41, P = 0.001) excretion than those with GSD-III and GSD-IX. GSD-I patients (n = 18) also had significantly higher Cinulin (F = 5.57, P = 0.009), but CPAH did not differ (F = 0.77, NS). Renal function was normal in GSD-III and GSD-IX patients. In GSD-I, Cinulin (r = -0.51, P = 0.03) and NAG excretion (r = -0.40, P = 0.03) were inversely correlated with age, whereas albumin excretion was positively correlated with age (r = +0.41, P = 0.03). RBP and calcium excretion were generally high throughout all age groups. Hyperfiltration in GSD-I is associated with renal tubular proteinuria that occurs before the onset of significant albuminuria. Deficiency of glucose-6-phosphatase within the proximal renal tubule may primarily cause tubular dysfunction, glomerular hyperfiltration being a secondary phenomenon.     

Occupational exposure to mercury in dentistry and dentist mortality

In response to public concern, Health Canada recently conducted a review of amalgam safety and released a position statement entitled The Safety of Dental Amalgam. Essentially, the department has concluded that the levels of mercury absorbed by the body due to the release of mercury vapor from amalgam restorations, while detectable, do not approach those recognized to cause illness. It has therefore confirmed that amalgam restorations can be used safely in most patients, with some notable caveats. Despite Health Canada's position statement in support of amalgam, patient doubts about amalgam safety remain, including the tenuous hypothesized link between amalgam restorations and specific diseases. This article reviews the available studies of dentist mortality to identify possible links between mercury exposure and negative health effects. A lack of evidence to suggest a detrimental health outcome in dentists who are occupationally exposed to higher levels of mercury than their patients, and are known to have higher levels of mercury in their blood, provides an important reassurance concerning the safety of amalgam. The reviewed data indicates that the 10 leading causes of death in the United States and Canada are the same for both dentist and non dentist population groups, and that the percentage of deaths by the same cause are remarkably similar. By 1975, the year of the most recent U.S. study, the average age at death for white male dentists was about three years higher than for all adult white males. Although suicide standard mortality rates are known to be higher for dentists, suicide deaths have also been shown to be a factor in many other occupations, particularly those where there is easy access to drugs. Although updated actuarial data for dentist mortality are needed, the available data indicate no reduction in the life expectancy of practising dentists, nor any specific or disproportionate rates of disease associated with high mercury exposure. In fact, the available mortality studies are generally optimistic about the health of dentists, which should reassure patients about the safety of dental amalgam.