Factors affecting blood mercury concentrations in practicing dentists

Dental caries in the peruvian police population

Background

Dental caries is a multifactorial disease that affects the general population. After reviewing the scientific literature, no studies were found on the index of decayed, missing and filled teeth (DMFT) in the Peruvian police population. The objective was to evaluate the DMFT index and severity level of the disease in police personnel of the Ancash region, Peru.

Material and Methods

Cross-sectional prevalence study. The medical records of the police personnel in activity were reviewed and each subject was examined from May 2012 to May 2013. The study was authorized by the Director of the PNP-Huaraz Ancash Polyclinic as part of the activities of the civil SERUMS personnel in the area of odontology. The sample was census with 925 subjects. The data was systematized following the methodology recommended by the World Health Organization (WHO). The statistics were analyzed by Chi square test with significance p<0.05, Pearson test and ANOVA.

Results

The prevalence of caries in the police population was 73.4%. The DMFT index was 10.63 ± 4.96 (p<0.01). The severity of the disease in relation to age was 0.77 ± 0.41 with a high risk in this population. The DMFT index in females 128/925 and males 797/925 was 10.43 and 10.67 respectively. There is an inversely proportional relationship in the number of teeth filled with dental amalgam in policemen older than 35 years versus the number of teeth sealed with material other than dental amalgam in policemen under 35 years. Only 0.8% 7/925 had dental prostheses and 58.6% (542/925) of the subjects needed oral rehabilitation.

Conclusions

The severity of dental caries is high, strategies are required to improve intervention in this sector, developing effective programs in oral health in the short, medium and long term.

Key words:Dental caries severity, oral health, dental caries prevalence, peruvian police.

Use of Mercury in Dental Silver Amalgam: An Occupational and Environmental Assessment

The objective of this study was to assess the occupational exposure to mercury in dentistry and associated environmental emission in wastewater of Lahore, Pakistan. A total of ninety-eight blood samples were collected comprising 37 dentists, 31 dental assistants, and 30 controls. Results demonstrate that the dentistry personnel contained significantly higher mean concentration of mercury in their blood samples (dentists: 29.835 µg/L and dental assistants: 22.798 µg/L) compared to that of the controls (3.2769 µg/L). The mean concentration of mercury was found maximum in the blood samples of older age group (62.8 µg/L) in dentists and (44.3 µg/L) in dental assistants. The comparison of mercury concentration among dentists, dental assistants, and controls (pairing based on their ages) revealed that the concentration increased with the age and experience among the dentists and dental assistants. Moreover, the mercury concentration in all the studied dental wastewater samples, collected from twenty-two dental clinics, was found to be exceeding the recommended discharge limit of 0.01 mg/L. Therefore, we recommend that immediate steps must be taken to ensure appropriate preventive measures to avoid mercury vapors in order to prevent potential health hazards to dentistry personnel. Strong regulatory and administrative measures are needed to deal with mercury pollution on emergency basis.

Evaluation of environmental and occupational exposure to mercury among Iranian dentists

The purpose of the study was to evaluate the environmental and occupational exposure to mercury (Hg), and to examine the various parameters, which contribute to high levels of mercury of Iranian dentists in Tehran. One-hundred hair and nail samples were collected from dentists. In addition, fifty samples from a control group and twenty-five additional samples from dental nurses were taken for comparison. The survey included a structured questionnaire designed to provide information about the parameters that influenced their occupational and environmental exposure to Hg. Overall mean concentrations in the hair and nails of the dentists was 2.84+/-0.47 and 3.56+/-0.53 mg/kg dry wt respectively. The equivalent values were 0.61+/-0.07 mg/kg in hair and 0.39+/-0.06 mg/kg in nails for the control group. In addition, mean concentrations in the dental nurses were 0.92+/-0.23 and 1.77+/-0.51 mg/kg in hair and nails respectively. The study showed that use of masks had a significant effect on Hg levels (p=0.02 for hair and p=0.03 for nails) and use of gloves only had significant effect on nails Hg (p=0.05). Hg concentrations in nails were significantly lower among the dentists who always used gloves and masks. Also, fish consumption and number of patients visited per day had a significant effect on hair (p=0.02 and p=0.02 respectively) and nails (p=0.03 and p=0.02 respectively) Hg. On the other hand, there was a significant effect of age in relation to Hg concentration in the hair and nails of the dentists (p=0.006 for hair and p=0.01 for nails). Multiple regressions were computed between hair Hg and the various assessed variables. The only positive results were between Hg concentration and masks for the dentists (p=0.03), and Hg concentration and the number of fish meals for the control group (p=0.009).

A validated cold vapour-AAS method for determining mercury in human red blood cells

A cold vapour-atomic absorption spectrometry (CV-AAS) method for determining mercury in dental students and clinical teaching staff red blood cells at a dental school using amalgam as a restorative material has been validated. A number of blood samples (n = 122) from dental students in years I to V, clinical teachers in restorative dentistry and controls were collected and analysed. Accuracy, linearity, precision (repeatability and reproducibility) and robustness of the method have been determined, and detection and quantification limits have been calculated. Linearity of response was verified for concentrations ranging from 5 to 40 microgL(-1) of mercury. Correlation coefficient of the calibration straight lines was always >/=0.99. Intra-day precision of the method gave coefficient of variation (CV) of 5.51%. Inter-day precision of the method calculated after analysis of five different concentrations of mercury standard solutions by the same analyst in different days and by two different analysts in different days gave coefficient of variation 4.89 and 5.44%, respectively. The accuracy of the method was calculated a CRM NIST 966 (toxic metals in bovine blood) total amount of mercury was found a concentration of 28.83 +/- 2.2 microgL(-1). Recovery was 89.27%. Robustness of the method evaluated by changing different experimental conditions under which analyses performed, fractional factorial design was done for assessing robustness of the method. Root mean square error was found out as 1.56. Limits of detection and quantification were 1.84 and 4.03 microg of Hg per litre of sample, respectively. Results show the suitability of the method for direct measurement of mercury in red blood cells and the importance of the working conditions for people dealing with amalgam at a dental school.

The relationship between amalgam restorations and mercury levels in male dentists and nondental health professionals

OBJECTIVES

The objectives of this study were: (1) to compare the mercury levels in general dentists with the mercury levels in other health professionals using toenail clippings as a biomarker, (2) to identify risk factors associated with high mercury levels, and (3) to compare practice characteristics of dentists with high and low mercury levels.

METHODS

A sample of 579 men was randomly selected from the 33,737 men participating in the Health Professionals Follow-up Study who had provided toenail samples in 1987. A questionnaire was sent to these male subjects in 1991 to obtain information on fish consumption, toothbrushing frequency, number of teeth, number of amalgam restorations, general practice or specialty status, number of amalgam restorations placed and removed per week, mercury storage and handling procedures, and mercury spillage incidents. A measure of long-term mercury exposure was obtained from toenail samples using neutron activation analysis for the 410 respondents (71% response rate). The 90th percentile mercury level in toenails (0.88 ppm) was selected as the threshold for elevated toenail mercury level.

RESULTS

No relationship was found between the number of dental amalgams and toenail mercury levels among general dentists, dental specialists, and nondental health professionals. General dentists were found to have more than twice the level of mercury in toenails than nondental health professionals (mean level = 0.94 vs 0.45) and 60 percent higher than dental specialists (mean = 0.59). The combined use of disposable capsules and water storage of scrap amalgam appeared to reduce the risk of elevated mercury levels. Regardless of professional status, consumption of tuna and saltwater fish were the primary exposure factors that were positively associated with toenail mercury levels.

CONCLUSIONS

As shown by the associations with dental profession and fish consumption, the mercury content of toenails is a stable biomarker of cumulative long-term mercury exposure. The lack of association between nail mercury levels and number of amalgam restorations suggests that avoidance of mercury amalgam restorative materials cannot be justified by the presence of mercury released from dental amalgams.

Blood mercury levels of dental students and dentists at a dental school

OBJECTIVE

To determine the blood mercury levels in dental students and clinical teaching staff in a dental school using amalgam as a restorative material.

SETTING

A dental school in Ege University, Turkey surveyed during one academic year.

SUBJECTS AND METHODS

Cross-sectional study of groups of dental students (n=92) in years I to V, clinical teachers in restorative dentistry (n=16) and controls (n=14). Mercury concentration was estimated in venous blood samples using a cold vapour atomic absorption method at the commencement and end of the academic year. Daily air mercury levels were determined in clinical and teaching areas by measuring the darkening of palladium chloride discs using spectrophotometry.

RESULTS

There were statistically significant increases (p<0.001) in plasma mercury concentration between measurements in all groups at the end of the academic year. Red cell mercury levels were also consistently elevated. Although the highest levels of mercury were recorded in persons working with amalgam, increased levels were also found in subjects working in the teaching classrooms but not with amalgam (controls and first year students).

CONCLUSION

Increased mercury levels appeared to be due to background exposure from spillage of mercury and amalgam residues on floors. Increased mercury hygiene and regular control of working atmosphere should be implemented to prevent mercury exposure in the dental pre-clinical laboratory.

Dental amalgam: update on safety concerns. ADA council on Scientific Affairs

This report of the Council on Scientific Affairs reviews and discusses recent studies concerning the safety of dental amalgam, with an emphasis on studies that have been published since the 1993 review of dental amalgam by the U.S. Public Health Service Committee to Coordinate Environmental Health and Related Programs. The Council concludes that, based on currently available scientific information, amalgam continues to be a safe and effective restorative material.

Mercury concentrations in urine and whole blood associated with amalgam exposure in a US military population

Minute amounts of mercury vapor are released from dental amalgams. Since mercury vapor is known to be associated with adverse health effects from occupationally exposed persons, questions regarding the margin of safety for exposure to mercury vapor in the general population continue to be raised. To address this issue, one needs information regarding exposure to mercury vapor from dental amalgam fillings and its possible consequences for health in the general population. The NIDR Amalgam Study is designed to obtain precise information on amalgam exposure and health outcomes for a non-occupationally-exposed population of US adults. One hypothesis was that in a generally healthy population a significant association between amalgam exposure and Hg levels in urine and/or whole blood could be detected. The cohort investigated was an adult military population of 1127 healthy males. Their average age was 52.8 years, and their ages varied from 40 to 78 years. Ninety-five percent of the study participants were white males, and slightly over 50% had some college education. Five percent were edentulous. The dentate participants, on average, had 25 natural teeth, 36.9 decayed or filled surfaces (DFS), and 19.9 surfaces exposed to amalgam, with amalgam exposure varying from 0 to 66 surfaces. Their average total and inorganic urinary mercury concentrations were 3.09 microg/L and 2.88 microg/L. The average whole-blood total and inorganic mercury concentrations were 2.55 microg/L and 0.54 microg/L. Significant correlations were detected between amalgam exposure and the total (r = 0.34, p < 0.001) and inorganic 0.34 (r = 0.34, p < 0.001) urinary mercury concentrations on the original scale. Stronger correlations were found for total (r = 0.44, p < 0.001) and inorganic (r = 0.41, p < 0.001) urinary Hg on the log scale, as well as for creatinine-corrected total (r = 0.43, p < 0.001) and inorganic (r = 0.43, p < 0.001) urine concentrations. In whole blood, statistically significant, but biologically weak, correlations were detected for total (r = 0.09, p = 0.005) and inorganic (r = 0.15, p < 0.001) Hg concentrations, respectively. Based on these cross-sectional data, it is estimated that, on average, each ten-surface increase in amalgam exposure is associated with an increase of 1 microg/L mercury in urine concentration.

[Illnesses caused by amalgam?]

BACKGROUND

As side effects of dental amalgam have been mentioned allergy, oral lichen, electro-galvanism, amalgam tattoos of gingiva or oral mucosa, and undesirable esthetics. Patients with amalgam restorations show increased mercury levels in different body fluids compared to amalgam-free controls. An intoxication due to dental amalgam fillings, however, is not to be expected-despite equivocal statements in the literature.

SCIENTIFIC RESULTS

In contrast, recent studies revealed that dental amalgam contributes to mercury exposure less than assumed few years ago. Therefore, amalgam will stay an option as a restorative material in future. The removal of intact amalgam fillings in the intention of "detoxification" is not science-based.

CONCLUSION

Successful caries prevention (e.g. due to the widespread use of fluoride) and the further development of esthetic restorative materials based on composite resins will limit the utilisation of amalgam. Thus, alternative materials have not been shown to have a lower rate of side effects (e.g. allergy) compared to amalgam.

Environmental issues in dentistry--mercury. FDI Commission

One of the consequences of placing amalgam restorations is that mercury is required for the trituration process. In turn, this raises the issue of the possible environmental impact of mercury. This report considers ways in which any impact can be modified and reduced by careful attention to mercury usage and hygiene in the dental practice, the use of filters and separators in waste water pipes and the appropriate disposal of waste contaminated with amalgam. The total amount of mercury discharged into the environment varies considerably in different parts of the world due to both natural and human activities. The extent to which dentistry adds to this total also varies according to local circumstances and requirements. Recommendations are given for further development of ways to reduce mercury discharge and for further research into the environmental impact of the metal.

Brain mercury in neurodegenerative disorders

BACKGROUND

Trace element neurotoxicity has long been invoked as an etiologic factor for Alzheimer's disease. This study was conducted to determine the concentrations of mercury in seven different brain regions from deceased patients histologically confirmed with Alzheimer's disease or multiple sclerosis as compared to control subjects without known central nervous system and renal disorders. Brain mercury concentrations in all deceased subjects can arise from amalgam restorations, diet, and the working environment.

METHODS

Autopsy frozen specimens (control, Alzheimer's disease and multiple sclerosis) from seven brain regions, which included frontal cortex, temporal cortex, occipital cortex, putamen, hippocampus, corona radiata and corpus callosum were assayed for the concentrations of selenium using instrumental neutron activation analysis and mercury using radiochemical neutron activation analysis.

RESULTS

We found that the concentrations of mercury and the mercury/selenium molar ratios were significantly lower in the hippocampi of multiple sclerosis patients as compared to aged-matched controls. However, no statistically significant differences were detected for the concentrations of mercury and the mercury/ selenium molar ratios for the remaining six brain regions among these groups.

CONCLUSIONS

Since brain mercury concentrations from deceased subjects with either Alzheimer's disease or multiple sclerosis are not significantly higher than controls, the present study provides no scientific support that mercury plays a significant role in the pathogenesis of these neurologic disorders.

Factors contributing to mercury exposure in dentists

Although mercury exposure levels among dentists have been steadily decreasing, occupational mercury exposure among dental professionals continues to be a matter of interest. This study examined personal professional and office characteristics of dentists to determine which factors contribute most to exposure. The resulting information will help dental professionals change their practices to minimize unnecessary exposure to elemental mercury.

Behavioral effects of low-level exposure to elemental Hg among dentists

Exposure thresholds for health effects associated with elemental mercury (Hg degree) exposure were examined by comparing behavioral test scores of 19 exposed (mean urinary Hg = 36 micrograms/l) with those of 20 unexposed dentists. Thirty-six micrograms Hg/l is 7 times greater than the 5 micrograms Hg/l mean level measured in a national sample of dentists. To improve the distinction between recent and cumulative effects, the study also evaluated porphyrin concentrations in urine, which are correlated with renal Hg content (a measure of cumulative body burden). Subjects provided an on-site spot urine sample, were administered a 1-h assessment consisting of a consent form, the Profile of Mood Scales, a symptom and medical questionnaire, and 6 behavioral tests: digit-span, symbol-digit substitution, simple reaction time, the ability to switch between tasks, vocabulary, and the One Hole Test. Multivariate regression techniques were used to evaluate dose-effects controlling for the effects of age, race, gender and alcohol consumption. A dose-effect was considered statistically significant below a p value of 0.05. Significant urinary Hg dose-effects were found for poor mental concentration, emotional lability, somatosensory irritation, and mood scores. Individual tests evaluating cognitive and motor function changed in the expected directions but were not significantly associated with urinary Hg. However, the pooled sum of rank scores for combinations of tests within domains were significantly associated with urinary Hg, providing evidence of subtle preclinical changes in behavior associated with Hg exposure. Coproporphyrin, one of three urinary porphyrins altered by mercury exposure, was significantly associated with deficits in digit span and simple reaction time.(ABSTRACT TRUNCATED AT 250 WORDS)

Fractional mercury levels in Brazilian gold refiners and miners

A field study survey of individuals residing in the region of Para, Brazil, was conducted to determine fractional mercury levels in individuals at risk for exposure in the Brazilian Amazon region. Subjects with a history of exposure to mercury either in the gold mining or refining industry, or exposure to these processes through proximity were included. Three groups were identified as either having recent (less than 2 d since last exposure), intermediate (less than 60 d), or remote (greater than 60 d) exposure to mercury vapors. Fractional blood and urinary mercury levels were assessed for these groups. Group I (recent) had the highest geometric mean blood 24.8 (SD 44.1, range 7.6-158.8) micrograms/L and urine 75.6 (SD 213.4, range 6.5-735.9) micrograms/g-cr (microgram mercury per gram of creatinine) mercury; intermediate (group II) geometric mean blood 7.6 (SD 5.5, range 2.2-19.4) micrograms/L and urine levels 23.8 (SD 84.0, range 7.8-297.0) micrograms/g-cr; the lowest levels in remote exposure (group III): geometric mean blood 5.6 (SD 3.3, range 3.1-14.3) micrograms/L and urine 7.0 (SD 9.8, range 3.1 to 32.9) micrograms/g-cr. The fraction of organic was lowest in group I (32.4%), higher in group II (65.7%), and highest in group III (72.2%). While the frequency of symptoms was comparable in the recent and intermediate groups (2.6 mean, SD 2.3, range 0-8, and 3.1 mean, SD 1.9, range 0-7, symptoms per patient), those with remote exposure demonstrated the highest rate of reporting (6.4 mean, SD 4.1, range 0-11, symptoms per patient). There is significant exposure to mercury for those working in or living near the mining and refining industry. Blood and urine levels are a better marker of recent than remote exposure. The fraction of organic mercury increases with time since exposure. Symptoms may be persistent and low levels of blood and urine mercury do not exclude remote or cumulative toxicity.

Determination of blood mercury concentrations in Alzheimer's patients

Trace element neurotoxicity can be an etiologic factor for Alzheimer's disease. This cross sectional clinical study determined blood mercury in patients with diagnosed Alzheimer's disease as compared to control subjects without known central nervous system and renal disorders. Unique within the confines of a nursing home, all subjects were exposed to the same environment and consumed a diet without fish and seafood for a period of three months prior to the study. The results of this study show that blood mercury concentrations detected in subjects with Alzheimer's disease were not statistically different than that of control subjects. Ratios of blood mercury to blood selenium were also determined and no statistical difference was found between these two groups.

Physiological and toxicological changes in the skin resulting from the action and interaction of metal ions

The human environment contains more than 50 metal or metalloid elements. At least 15 are recognized as trace elements, with zinc, calcium, copper, magnesium, and iron having specific roles in skin morphogenesis and function. The present review focuses on the presumed role of metal ions in the skin, their competition for carrier proteins, and membrane receptors. Evidence presented shows that the balance of trace metal ions is critical for normal skin and repair mechanisms following injury. Xenobiotic ions can impair this balance, leading to pathological change. The skin acts as an organ of elimination of excess trace metals and xenobiotic ions from the body, but mechanisms of voidance vary for different metals. Metal ions are an important cause of allergies, and evidence is presented to show that the majority of metals or metal compounds can induce allergic changes. Except for chromium and nickel, which are among the most common human allergens, animal models have provided little information. At least cadmium, thorium, lead, chromium, nickel, beryllium, and arsenic and proven or putative carcinogens in animals or humans on the basis of cytological or epidemiological evidence. However, only arsenic exhibits a clear predilection for the skin. Other metals such as gold can induce subcutaneous sarcoma following injection, but the relevance of this observation in terms of human occupational risk is discounted.

The level of mercury in human dental plaque and interaction in vitro between biofilms of Streptococcus mutans and dental amalgam

Mercury levels (micrograms/mg dry weight) in dental plaque from amalgam and enamel surfaces in human subjects with amalgam restorations were (range, mean, SD) 0.5-1.31, 0.72, 0.34 and 0.01-0.54, 0.2, 0.19, respectively. The levels of mercury in plaque from amalgam surfaces were significantly higher than those from plaque on enamel (p < 0.001). No mercury was detected in plaque from subjects without amalgam restorations. The mean level of mercury in a 24-hour collection of plaque was 2 micrograms (median, 1.8 micrograms), an amount close to those calculated by other workers (1.2-1.7 micrograms) for the amount of mercury liberated in the mouth from amalgam restorations in 24 h. Freshly prepared amalgam liberated relatively large amounts of mercury into culture broth in the first 24 h of exposure; subsequently, the levels declined except in the presence of Streptococcus mutans. In vitro, biofilms of Streptococcus mutans facilitated the release of mercury from freshly prepared amalgam, in what appeared to be a cyclical fashion. Amalgam aged for two years did not release mercury, even when supporting the growth of an S. mutans biofilm. The resistance of aged amalgam was attributed to the presence of a passive tarnish layer. The mercury released by the biofilm had an effect on the composition of the biofilm. The biofilms on fresh amalgam had significantly lower levels of carbohydrate (p < 0.001-p < 0.01) and protein (p < 0.001-p < 0.02) than did biofilms on aged amalgam and on control stainless steel wires.

Annual review of selected dental literature: report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The annual review of selected dental literature this year cites 384 published papers and reports. This year's review contains more editorial comment than reviews of years passed. New data on the biological responses to materials is emphasized in several sections. Observations on new compounds able to prevent plaque formation are presented. Clinically relevant advances in knowledge concerning the etching of different tooth structures are reported along with the effect of etching procedures on the dental pulp. Evaluation of periodontal diseases in all age groups is a topic. Limitations of current diagnostic techniques in periodontal disease, temporomandibular disorders, and implant therapy are included. There are new views on the use of dental amalgam. The future use of dental mercury is predicted. Interest in new ceramic systems is indicated as the demand for esthetics continues. Clinical information is emphasized over scientific information throughout this year's review.