Amalgam Treatment Research Articles

Dental sealants and composite restorations and longitudinal changes in immune function markers in children

Resins used in dental composites, derived from bisphenol-A (BPA), have been shown to alter immune cells. The objective of this study was to explore children's immune function changes in relation to resin composite treatment. We conducted secondary data analysis of the New England Children's Amalgam Trial immune function substudy (N=59). Immune function was measured pre-treatment and up to five times post-treatment through 5-year follow-up. Multivariable generalized linear regression models were used to estimate the association between three classes of resin composites (bisphenol-A-diglycidyl-dimethacrylate [BisGMA]-based flowables used for preventive sealants; urethane dimethacrylate [UDMA]-based compomer restorations; bisGMA-based restorations) and changes in immune function markers measured annually. Total white blood cell counts and responsiveness of T cells or neutrophils were not appreciably altered by composite treatment levels. Changes in B cell responsiveness were greater throughout follow-up among children with more bisGMA-based composite restorations, which opposed findings for amalgam treatment levels. Monocyte responsiveness changes were decreased at 6months with greater treatment, but not over longer follow-up. Results of this analysis showed no overt immune function alterations associated with resin composites. Additional research regarding lymphocyte activation may be warranted given the consistency of results within these analyses and with a prior study showing increased B cell activation.

부산, 경남 일부 지역 주민들의 생선 섭취량과 혈중 수은 농도의 관련성

본 연구는 직업적으로 수은에 노출되지 않는 일반 인구 군에서 생선 섭취량과 혈중 수은 농도 사이의 관련성을 파악하기 위하여 수행되었다. 이를 위하여 부산광역시 2개 동과 남해군 3개 마을에 거주하는 사람들 중 본 연구 참여에 동의한 484(남자: 134명, 여자: 350명)명을 최종 연구대상으로 하였다. 설문조사는 2009년 6월 말부터 7월초까지 연구 참여 희망자들을 대상으로 훈련된 조사자가 면접설문조사를 실시하였다. 설문 조사의 주요 내용은 성별, 연령, 학력, 결혼상태, 직업, 현재 흡연 여부, 현재 음주 여부, 일주일간 생선 섭취량, 아말감 치료, 거주지역 등이었다. 단변량 분석에서 성별, 나이, 결혼상태, 현재 음주 여부, 일주일간의 생선 섭취량, 그리고 거주지역이 혈중 수은 농도와 유의한 관련성이 있었다. 혈중 수은 농도를 종속 변수로 한 다중선형회귀분석에서 일주일간의 생선 섭취량, 그리고 거주지역이 혈중 수은 농도와 유의한 관련성이 있었다. 생선 섭취량과 혈중 수은 농도 간에는 통계적으로 유의한 관련성이 있다. 앞으로 혈중 수은 농도와 건강 장애간의 관련성을 비롯한 추가적인 연구를 통하여 생선 섭취와 연관된 수은 노출 기준, 실제적인 생선 내 수은 잔류 기준, 생선 섭취빈도와 생선 섭취량에 관한 여러 가지 권고안들을 마련하기 위한 근거 기반을 마련해야 할 것이다. Objectives: The objective of this study was to identify the relationship between fish consumption and blood mercury levels in a sample of adult Koreans. Methods: The study subjects were 299 residents of Busan (male: 65, female: 234) and 185 residents of Namhae (male: 69, female: 116), South Korea. Demographic characteristics, current smoking, current drinking, fish consumption per week, past history of amalgam treatment, and residential district were recorded by trained interviewers in June and July, 2009. We considered a portion of fish to be equivalent to 70 gm weight, and calculated amounts of fish consumed per week. Using chi-square tests, t-tests, ANOVA, and multiple linear regression analysis, we estimated the relationships between blood mercury levels and amount of fish consumed per week and other factors. Results: The mean blood mercury level of our subjects was 6.61 <TEX>${\mu}g/L$</TEX>, higher than the criterion defined by the United States Environmental Protection Agency (EPA) (5.8 <TEX>${\mu}g/L$</TEX>). In multiple linear regression analysis, residential district and amount of fish consumed per week were associated with blood mercury levels. However, marital status, current drinking, and gender, and age were not associated with blood mercury levels. Conclusions: In conclusion, we suggest the implementation of systematic and periodic population-based studies to decrease the risks of mercury poisoning among South Koreans who consume fish as a regular part of the diet.

Dental composite restorations and neuropsychological development in children: Treatment level analysis from a randomized clinical trial

BackgroundResin-based dental restorations may intra-orally release their components and bisphenol A. Gestational bisphenol A exposure has been associated with poorer executive functioning in children. ObjectivesTo examine whether exposure to resin-based composite restorations is associated with neuropsychological development in children. MethodsSecondary analysis of treatment level data from the New England Children's Amalgam Trial, a 2-group randomized safety trial conducted from 1997 to 2006. Children (N=534) aged 6–10 y with ≥2 posterior tooth caries were randomized to treatment with amalgam or resin-based composites (bisphenol-A-diglycidyl-dimethacrylate-composite for permanent teeth; urethane dimethacrylate-based polyacid-modified compomer for primary teeth). Neuropsychological function at 4- and 5-year follow-up (N=444) was measured by a battery of tests of executive function, intelligence, memory, visual-spatial skills, verbal fluency, and problem-solving. Multivariable generalized linear regression models were used to examine the association between composite exposure levels and changes in neuropsychological test scores from baseline to follow-up. For comparison, data on children randomized to amalgam treatment were similarly analyzed. ResultsWith greater exposure to either dental composite material, results were generally consistent in the direction of slightly poorer changes in tests of intelligence, achievement or memory, but there were no statistically significant associations. For the four primary measures of executive function, scores were slightly worse with greater total composite exposure, but statistically significant only for the test of Letter Fluency (10-surface-years β=−0.8, SE=0.4, P=0.035), and the subtest of color naming (β=−1.5, SE=0.5, P=0.004) in the Stroop Color-Word Interference Test. Multivariate analysis of variance confirmed that the negative associations between composite level and executive function were not statistically significant (MANOVA, P=0.18). Results for greater amalgam exposure were mostly nonsignificant in the opposite direction of slightly improved scores over follow-up. ConclusionsDental composite restorations had statistically insignificant associations of small magnitude with impairments in neuropsychological test change scores over 4- or 5-years of follow-up in this trial.

Dental Composite Restorations and Psychosocial Function in Children

Resin-based dental materials may intraorally release their chemical components and bisphenol A. The New England Children's Amalgam Trial found that children randomized to amalgam had better psychosocial outcomes than those assigned to composites for posterior tooth restorations. The objective of this study was to examine whether greater exposure to dental composites is associated with psychosocial problems in children. Analysis of treatment-level data from the New England Children's Amalgam Trial, a 2-group randomized safety trial comparing amalgam with the treatment plan of bisphenol A-glycidyl methacrylate (bisGMA)-based composite and urethane dimethacrylate-based polyacid-modified composite (compomer), among 534 children aged 6 to 10 years at baseline. Psychosocial function at follow-up (n = 434) was measured by using the self-reported Behavior Assessment System for Children (BASC-SR) and parent-reported Child Behavior Checklist (CBCL). Children with higher cumulative exposure to bisGMA-based composite had poorer follow-up scores on 3 of 4 BASC-SR global scales: Emotional Symptoms (β = 0.8, SE = 0.3, P = .003), Clinical Maladjustment (β = 0.7, SE = 0.3, P = .02), and Personal Adjustment (β = -0.8, SE = 0.2, P = .002). Associations were stronger with posterior-occlusal (chewing) surfaces, where degradation of composite was more likely. For CBCL change, associations were not statistically significant. At-risk or clinically significant scores were more common among children with greater exposure for CBCL Total Problem Behaviors (16.3% vs 11.2%, P-trend = .01) and numerous BASC-SR syndromes (eg, ≥ 13 vs 0 surface-years, Interpersonal Relations 13.7% vs 4.8%, P-trend = .01). No associations were found with compomer, nor with amalgam exposure levels among children randomized to amalgam. Greater exposure to bisGMA-based dental composite restorations was associated with impaired psychosocial function in children, whereas no adverse psychosocial outcomes were observed with greater urethane dimethacrylate-based compomer or amalgam treatment levels.

전남지역 일부 대학생 모발 중 수은 농도에 관한 연구

This study analysed the mercury concentration in the hair of 62 students (male : 21, female : 41) of D university in Najusi, Jeon-Nam area. Also, questionnaire, which developed by NIES, were completed by the students. According to the questionnaire, most of the students had a higher intake of meat than that of fish. Also, among the students, there were many smokes and many had dental treatment with amalgam. Based on the gender, female showed 1.024 <TEX>${\mu}g/g$</TEX> and male showed 0.882 <TEX>${\mu}g/g$</TEX> of the mercury concentration. This means that female students had higher level of mercury in their hair, but it was not a significant statistic difference. Comparing by the intake frequency of meat, processed food stuffs, protein foods, it shows the more they at the higher mercury concentration was observed. According to the intake frequency of fish, when the number of times they intake increased, the mercury concentration was higher. Under one time was 0.857 <TEX>${\mu}g/g$</TEX> and twice or more times were 1.152 <TEX>${\mu}g/g$</TEX>, which showed a significant statistical difference (p<0.05). Depending on the Life style, the mercury concentration in the hair was high with workout, outdoor activities, and direct smoking. The mercury concentration in the hair showed no difference for whether they received amalgam treatment but the personal dietary habit and the Living condition affects strongly on the mercury concentration level.

Urinary Porphyrin Excretion in Children with Mercury Amalgam Treatment: Findings from the Casa Pia Children's Dental Amalgam Trial

Increases in the urinary concentrations of pentacarboxyl- and coproporphyrins and the appearance of the atypical precoproporphyrin have been defined in relation to mercury (Hg) body burden in animal studies, and this change in the porphyrin excretion pattern has been described as a biomarker of occupational Hg exposure and toxicity in adult human subjects. In the present studies, urinary porphyrins were determined in relation to Hg exposure in children and adolescents, 8–18 yr of age, over the 7-yr course of a clinical trial designed to evaluate the neurobehavioral and renal effects of dental amalgam in children. Subjects were randomized to either dental amalgam or composite resin treatments. Urinary porphyrins and creatinine concentrations were measured at baseline and annually in all subjects. Results were evaluated using linear regression analysis. No significant differences between treatment groups (amalgam versus composite) were found when comparing all subjects for any of the porphyrins of interest. However, incipent amalgam treatment-specific increases were observed in the mean concentrations of penta-, precopro- and coproporphyrins especially when the analyses were restricted to younger subjects (8 to 9 yr old at baseline), and these increases were most apparent during yr 2 through 3 of follow-up, the period of highest mercury exposure from amalgam treatment. Based on the mean number of amalgam fillings received by children in this group (17.8), the renal Hg concentration associated with incipient increases in urinary porphyrins was estimated to be approximately 2.7 μg/g renal cortex. This value corresponds to an observed mean urinary Hg concentration of 3.2 μg/g creatinine, which is approximately fivefold less than that at which renal damage from Hg exposure is estimated to occur in children. These findings are consistent with growing evidence supporting the sensitivity of urinary porphyrins as a biological indicator of subclinical Hg exposure in children.

Nephrotoxicity, neurotoxicity, and mercury exposure among children with and without dental amalgam fillings.

A scientific review panel for the US Food and Drug Administration (FDA) recently identified the need for more data on the health risk of mercury exposure from dental amalgam among susceptible populations. We evaluated impacts of low-level mercury exposure on renal function and neurobehavioral and neuropsychological performance among children. Dental histories for 403 children aged 7-11 years in five schools from Xuhui, Shanghai were checked by dentists. Of them, 198 with confirmed amalgam fillings were recruited (exposure group). Reference children (N=205) were those who never had dental amalgam treatment. In May 2004, each child provided a urine sample for measurements of total mercury, N-acetyl-beta-D-glucosaminidase activity, microalbumin, and creatinine (Cr). The Child Behavior Checklist, Eysenck Personality Questionnaire, and an intelligence screening test were administered. The geometric mean urinary mercury concentration was 1.6 microg/g Cr for children with and 1.4 microg/g Cr for children without amalgam fillings. No differences were found between children with and without fillings for either renal function biomarker, or on neurobehavioral, neuropsychological, or intelligence tests. Although urinary mercury concentration was slightly elevated among children with amalgam fillings, we found no evidence of adverse effects on the outcomes evaluated. These results agree with those from recent trials in developed countries.

Biomarkers of kidney integrity in children and adolescents with dental amalgam mercury exposure: Findings from the Casa Pia children's amalgam trial

Mercury is toxic to the kidney, and dental amalgam is a source of mercury exposure. Few studies have evaluated the effects of dental amalgam on kidney function in a longitudinal context in children. Here, we evaluated urinary concentrations of glutathione S-transferases (GSTs) α and π as biomarkers of renal proximal and distal tubular integrity, respectively, and albumin as a biomarker of glomerular integrity in children and adolescents 8–18 years of age over a 7-year course of dental amalgam treatment. Five hundred seven children, 8–12 years of age at baseline, participated in a clinical trial to evaluate the neurobehavioral and renal effects of dental amalgam in children. Subjects were randomized to either dental amalgam or resin composite treatments. Urinary GSTs α and π, albumin, and creatinine concentrations were measured at baseline and annually in all subjects. Results were evaluated using linear regression analysis. GST-α concentrations were similar between treatment groups and in each sex and race (white vs. non-white) group in each follow-up year. GST-π levels tended upward over the course of follow-up by four- to six-fold. This increase was seen in all groups irrespective of the treatment, race, or gender. Females had GST-π levels approximately twice those of males at all ages. Albumin concentrations were constant throughout the follow-up period and did not differ by treatment, although females had 39% higher albumin levels than males. Additionally, we found no significant effects of amalgam treatment on the proportion of children with microalbuminuria (>30 mg/g creatinine). These findings are relevant within the context of children's health risk assessment as relates to the safety of mercury exposure from dental amalgam on kidney function. These data also provide normative values for sensitive indices of renal functional integrity that may serve in the evaluation of children and adolescents with renal disorders.

Contribution of Dental Amalgam to Urinary Mercury Excretion in Children: Woods et al. Respond

We are pleased to respond to Iavicoli and Carelli’s comments on our article (Woods et al. 2007). Iavicoli and Carelli question our use of creatinine adjustment; in previous studies, we addressed the pros and cons of this issue in depth (Heyer et al. 2007; Martin et al. 1996; Woods et al. 1998). In terms of the present study (Woods et al. 2007), instead of advocating one approach over the other, we presented data, where appropriate (e.g., Figure 2), as both adjusted and unadjusted measures to provide the reader access to both sets of results. Iavicoli and Carelli note only a slight difference in Figure 2 between comparisons of adjusted and unadjusted urinary Hg levels at year 7; in our article we explained the higher variability (not bias) in the unadjusted values. Because creatinine adjustment did not otherwise alter the urinary Hg findings in the study, as stated in our Figure 3 (Woods et al. 2007), we did not present adjusted values for data described in Figures 3 or 4. Iavicoli and Carelli’s comments about blood Hg levels are not relevant because we did not measure blood Hg concentrations in this study. Regarding Iavicoli and Carelli’s comment on “steady state,” data presented in our Figure 4 (Woods et al. 2007) allow the reader to discern the influence of additional amalgam treatment on Hg body burden over time, as inferred from annual urinary Hg levels. A comprehensive pharmacokinetic evaluation of Hg body burden was neither intended nor within the scope of this study. Iavicoli and Carelli speculate that Hg sulfide on teeth surfaces might have affected observed changes in urinary Hg levels; however, others (Brune 1986; Brune and Evje 1985; Gebel and Dunkelberg 1996) have clearly shown that sulfide (and other oxidation) layers are continuously removed by the effects of mastication, as well as by hot foods and liquids. These layers do regenerate but are in a constant state of flux. Because all of the amalgam used in this study (Woods et al. 2007) was of a single formulation, there would have been no variation in the tendency to form sulfide layers from amalgam treatment. Additionally, although there may have been some variation in oral pH among study subjects that could have influenced this process, Hg elimination still occurs at a relatively constant state. Therefore, we do not consider Hg sulfide film formation to be a significant factor in urinary Hg excretion over time. Iavicoli and Carelli question our use of “dose effect” to describe the relationship of amount of amalgam treatment received with urinary Hg concentration. However, we consider this depiction appropriate. Finally, Iavicoli and Carelli point out that the trend that children who received up to nine initial amalgam fillings but no subsequent treatment returned to pretreatment values within 1 year is not clear. This statement should have been “within 1 additional year” (i.e., by year 3 of follow-up). Urinary Hg levels were highest approximately 2 years after initial amalgam treatment for those with no subsequent treatment; those with ≥ 10 fillings at initial treatment and no subsequent treatment took > 3 years (approximately 5 years) to return to pretreatment levels. For Figure 4 (Woods et al. 2007), we obtained confidence intervals, but they were not included because of the clutter they created in the figures. Thus, the statements refer to trends and not statistical significance.

Contribution of Dental Amalgam to Urinary Mercury Excretion in Children

Woods et al. (2007) studied a group of children (n = 507) who were exposed by inhalation to elemental mercury (Hg0) from dental amalgam fillings. In the study, 253 subjects were exposed, whereas the remaining 254 children, the control group, were exposed to composite resin. We consider the experimental design of their study to be adequate, but we do have questions about their methods of data handling and interpretation. For example, we do not understand why instead of always using creatinine-adjusted Hg levels, they used—in some instances—unadjusted Hg levels. In fact, there is continuous alternation and exchange between the two biological concepts (i.e., between the unadjusted and the adjusted concentrations). There are at least three well-grounded and well-known reasons that creatinine adjustment is essential: a) urinary creatinine accounts for variations in 24-hr excretion (Aito et al. 1983); b) urinary creatinine adjustment reportedly reflects Hg blood levels (Smith et al. 1970) and possibly Hg body burden; and c) in the light of established knowledge, Hg blood levels reflect recent exposure (Piotrowski et al. 1975). Accordingly, the lack of significance between the Hg levels (not adjusted for creatinine) of the amalgam and the control subgroups at year 7, the final year of the study by Woods et al. (2007), is probably a bias that is indicated by the disappearance of overlapping if creatinine adjustment had been performed, as suggested by Aitio et al. (1983) as long as 25 years ago. Also, because no adjusted data were reported for male and female levels, the impact of such an adjustment cannot be conjectured by the reader. Subsequently this prevents accurate evaluation of the Hg level trend over the years. It should be pointed out that the data of Woods et al. (2007) do not allow us to extrapolate whether or not the exposed subgroup is in the steady state, because this condition depends on the time lag between urine collection and the last amalgam treatment(s). This limitation prevents an accurate interpretation of the decrease in urinary Hg levels over years. Geller (1976) reported that Hg sulfide can coat Hg0, thereby slowing down the release of Hg vapor. Although no specific study has determined whether this is true for amalgams, we cannot exclude that Hg oxidation may yield Hg sulfide on the amalgam surface. Woods et al. (2007) speculated about the decrease in Hg urinary excretion over years, but they did not consider the possibility of sulfide formation. Moreover, they did not explain the decrease in Hg levels over time after year 2 but simply stated that “the rate of urinary [Hg] excretion exceeds the rate of [Hg] exposure from dental amalgam.” The formation of a thin film of Hg sulfide on amalgam surfaces could be an explanation, especially since the Hg body burden—and consequently Hg urinary levels—may be either in the steady state or at an increasing elimination rate because of the addition of new fillings. Furthermore, we feel that the use of the term “dose–effect relationship” by Woods et al. (2007) is questionable. Also, it is not clear if the term “dose” refers to the number of additional amalgam fillings over the years or to the difference between means. Also, “effect” has a completely different meaning in toxicology. In this case, another term should be used to more accurately indicate the difference in two urinary Hg levels. In our opinion, “differential dose minus follow-up years” would be more appropriate in the text than “dose effect.” Woods et al. (2007) stated that in children who received “up to 9 initial amalgam fillings, urinary Hg returned to pre-treatment value within one year,” but this statement is not clear because this trend applies only to children who received 0–4 amalgam fillings at baseline but not to the group that received 5–9 [Figure 4; Woods et al. (2007)]. Finally, Woods et al. (2007) omitted error bars from their Figure 4; SE or SD could have been easily calculated by the theory of error propagation and would probably have addressed the discussion more accurately, or at least would have tempered some conclusions, especially with regard to confirmation of the “whole-body biological half-time of Hg on the order of 60–70 days.” This half-time is correct but there is a large margin of uncertainty based on the experimental data. In conclusion, although Woods et al. (2007) used a well-structured experimental design, their conclusions are not accurate because of their handling of the experimental results and their use of basic toxicology terminology.

국내 초등학생의 체내 총수은 농도 및 노출요인 조사

Mercury contamination and its health effects have become major concern of environmental health study in Korea. Mercury exposure of some group were investigated to get the accurate data for policy making and study. About 2,000 children at 26 elementary schools participated in this survey to evaluate the exposure levels and to investigate main exposure source of mercury. Analysis of mercury levels in the whole blood and urine samples were conducted and questionnaire survey was done about the factors influencing exposures simultaneously. Mercury exposure levels of domestic children were N.D. to 17.26 ppb in blood, 0.17 to <TEX>$21.67{\mu}g/g$</TEX>-creatinine in urine. The mean(arithmetic) levels are 2.42 ppb in blood and <TEX>$2.53{\mu}g/g$</TEX>-creatinine in urine. Both of them were below the recommendation levels of US EPA and German CHBM I <TEX>$5.8{\mu}g/l$</TEX> and <TEX>$5{\mu}g/l$</TEX> in blood, <TEX>$5{\mu}g/g$</TEX>-creatinine of German CHBM I in urine. But 1%, 0.51% of levels in blood exceed the level of CHBM I and US EPA, 8%, 0.85% of children were over the level of CHBM I and CHBM II in urine. Multi-valuable regression analysis showed that the existence of road near the residence in addition to the preference for fish have significance with blood mercury exposure level of domestic children. The existence of factory near the house and the experience of dental amalgam treatment had statistical relations with urine mercury level.

The contribution of dental amalgam to urinary mercury excretion in children.

BackgroundUrinary mercury concentrations are widely used as a measure of mercury exposure from dental amalgam fillings. No studies have evaluated the relationship of these measures in a longitudinal context in children.ObjectiveWe evaluated urinary mercury in children 8–18 years of age in relation to number of amalgam surfaces and time since placement over a 7-year course of amalgam treatment.MethodsFive hundred seven children, 8–10 years of age at baseline, participated in a clinical trial to evaluate the neurobehavioral effects of dental amalgam in children. Subjects were randomized to either dental amalgam or resin composite treatments. Urinary mercury and creatinine concentrations were measured at baseline and annually on all participants.ResultsTreatment groups were comparable in baseline urinary mercury concentration (~ 1.5 μg/L). Mean urinary mercury concentrations in the amalgam group increased to a peak of ~ 3.2 μg/L at year 2 and then declined to baseline levels by year 7 of follow-up. There was a strong, positive association between urinary mercury and both number of amalgam surfaces and time since placement. Girls had significantly higher mean urinary mercury concentrations than boys throughout the course of amalgam treatment. There were no differences by race in urinary mercury concentration associated with amalgam exposure.ConclusionsUrinary mercury concentrations are highly correlated with both number of amalgam fillings and time since placement in children. Girls excrete significantly higher concentrations of mercury in the urine than boys with comparable treatment, suggesting possible sex-related differences in mercury handling and susceptibility to mercury toxicity.

Mercury Intolerance in Relation to Superoxide Dismutase, Glutathione Peroxidase, Catalase, and the Nitroblue Tetrazolium Responses

Through percutaneous provocation with metallic mercury and phenyl mercuric acetate in patients stating the presence of subjective psychosomatic symptoms following dental amalgam treatment, it has been possible to categorize and score two extreme groups of patients, mercury-intolerant and mercury-tolerant patients reacting and not reacting, respectively, to low doses of mercury. The intolerant patients had a high psychosomatic score and the tolerant patients had a low or null score when exposed to low doses of the two mercury compounds. Determination of the scavenger enzymes superoxide dismutase, glutathione peroxidase, and catalase showed no significant differences between the mercury-intolerant and the mercury-tolerant patients and the controls. The activity of superoxide dismutase and the quantitative psychosomatic score elicited by either metallic mercury or phenyl mercuric acetate showed a positive correlation. On the other hand, analyses of the psychosomatic score and the areas under the curves of the nitroblue tetrazolium test response showed negative correlations. The results indicate that the oxidative metabolism and, in particular, superoxide dismutase may be perturbed in mercury-intolerant patients.

Replacement risk of amalgam treatment modalities: 15-year results

Objectives: This paper reports on the replacement risk of different treatment modalities for Class II amalgam restorations in a clinical trial of 15 years' duration. Methods: The performance of 1117 conventional Class II amalgam restorations in a controlled, longitudinal study were analysed using logistic regression with a random component. Primary variables regarding replacement risk were the treatment modality (cavity wall treatments) and alloy (conventional versus high copper). Secondly, the operator, type of tooth and type of restoration (MO/DO vs MOD) were considered. Results: Over 15 years, 17% of the restorations were replaced (true failures). The application of copalite varnish or silver suspension and the type of alloy did not reduce the replacement risk. Reduced risks were observed by providing a 90° cavosurface angle combined with a cavity wall finish. The operator and the type of restoration determine replacement risk to a significant extent. Conclusions: Additional treatment modalities do not necessarily reduce replacement risks of Class II amalgam restorations within 15 years, while clinical variables affect the risk of replacement to a certain degree.

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.

In vitro testing of dental materials by means of macrophage cultures: II. Effects of particulate dental amalgams and their constituent phases on cultured macrophages.

It is known that macrophages play an important role in the removal of foreign particulate matter from tissue. When powdered dental amalgam is introduced into the soft tissues an amalgam tattoo is formed due to the intracellular degradation of amalgam by macrophages and their polykaryons. It was therefore feasible to study the effects of particulate amalgams as well as their individual phases on macrophages in vitro. The parameters compared were rate of the phagocytosis, changes of cellular morphology, and release of lactate dehydrogenase (LDH) to demonstrate plasma membrane permeability. It was shown that all the alloys except the Sn8Hg particles (gamma 2-phase) and gamma 2-containing Revalloy were effectively phagocytized by macrophages, and the alterations in cellular morphology were slight during the first day. Prominent cellular damage was seen in cultures treated with particulate Ag2Hg3 (gamma 1-phase) and Revalloy for 1 week. A slight increase in LDH activity in the medium was seen one hour after the alloy treatment. The LDH activities due to the amalgam treatment increased in the order Dispersalloy less than Revalloy less than Sybraloy. Intraperitoneal phagocytosis did not cause any morphological changes in macrophages, but the per cent of phagocytosis was diminished.

STUDIES ON THE TOXICITY OF MERCURY (Hg Series No. 11)

In order to obtain a comprehensive picture of the dental staff (11 dental office in Tokyo area) whom how mercury from amalgam has influenced, the authors preformed a number of experiments which could be summarized as follows:1. Analyses of the urine of dentists, dental hygienists, dental nurses and dental technicians completed the picture of the mercury exposure of the dental staff. The colorimetric procedure of choice was carried by the dithizone method (a simplified method for determing mercury in urine) by Nishimura and Aoki.The mercury concentration in urine in 40 dental staff persons was 109.8μg/l in average, ranging from 6 to 588μg/l.2. High concentration of mercury was excreted in urine of those who had frequent chance of doing amalgam treatment (a dental hygienists and a nurse, each one case). The mercury concentration was each 332μg/l and 588μg/l.3. No relation was found between the dental career and urinary mercury concentration.4. A relation was observed between the frequency of doing amalgam treatment and the urinery mercury concentration, which was varied by good or poor air conditioning of dental offices.5. The air mercury concentration of the dental office in buildings was influenced by temperture and ventilation.The air concentration of mercury in the air conditioned office was 0.09mg/m3, the air of which was collected one meter apart from amalgam procedure spot.In case of two offices without air conditioning, the mercury concentration was each 0.15mg/m3 and 0.2mg/m3.6. Urinery mercury concentration of 5 persons whose amalgam procedure was mainly performed by means of hands, was 520, 250, 240, 70 and 180μg/l respectively.

The reduction of purines and pyrimidines

1. 1. The ultraviolet-absorption curves of various pyrimidines and purines have been compared before and after submitting to reduction by zinc, by sodium-mercury amalgam, and by electrolytic reduction at the dropping-mercury electrode (polarograph). After sodium-mercury amalgam treatment the maxima in the ultraviolet curves are entirely, or almost entirely, removed. 2. 2. Decomposition products such as ammonia or formaldehyde have been shown to be produced under such circumstances, and similar diazotizable amines are produced from adenine and hypoxanthine by sodium-mercury reduction and continued polarographic reduction. 3. 3. Although sodium-mercury amalgam is a stronger reducing agent than zinc, as shown by the relative decrease in the ultraviolet-absorption maxima, the substances xanthine, thymine, uracil, and 2-aminopyrimidine do not yield disintegration products, suggesting that these ring systems are not disrupted by its action.