Developmental dental defects in children exposed to PCBs in eastern Slovakia

Prenatal exposure to persistent organic pollutants and molar-incisor hypomineralization among 12-year-old children in the French mother-child cohort PELAGIE

BACKGROUND

Exceptional episodes of exposure to high levels of persistent organic pollutants have already been associated with developmental defects of enamel among children, but knowledge is still scarce concerning the contribution of background levels of environmental contamination.

METHODS

Children of the French PELAGIE mother-child cohort were followed from birth, with collection of medical data and cord blood samples that were used to measure polychlorinated biphenyls (PCBs), organochlorine pesticides (OCs), and perfluorinated alkyl substances (PFASs). At 12 years of age, molar-incisor hypomineralization (MIH) and other enamel defects (EDs) were recorded for 498 children. Associations were studied using logistic regression models adjusted for potential prenatal confounders.

RESULTS

An increasing log-concentration of β-HCH was associated with a reduced risk of MIH and EDs (OR = 0.55; 95% CI, 0.32-0.95, and OR = 0.65; 95% CI, 0.43-0.98, respectively). Among girls, intermediate levels of p,p'-DDE were associated with a reduced risk of MIH. Among boys, we observed an increased risk of EDs in association with intermediate levels of PCB 138, PCB 153, PCB 187, and an increased risk of MIH with intermediate levels of PFOA and PFOS.

CONCLUSIONS

Two OCs were associated with a reduced risk of dental defects, whereas the associations between PCBs and PFASs and EDs or MIH were generally close to null or sex-specific, with an increased risk of dental defects in boys. These results suggest that POPs could impact amelogenesis. Replication of this study is required and the possible underlying mechanisms need to be explored.

Use of Dental Defects Associated with Low-Dose di(2-Ethylhexyl)Phthalate as an Early Marker of Exposure to Environmental Toxicants

BACKGROUND

Markers of exposure to environmental toxicants are urgently needed. Tooth enamel, with its unique properties, is able to record certain environmental conditions during its formation. Enamel formation and quality are dependent on hormonal regulation and environmental conditions, including exposure to endocrine disrupting chemicals (EDCs). Among EDCs, phthalates such as di-(2-ethylhexyl) phthalate (DEHP) raise concerns about their contribution to various pathologies, including those of mineralized tissues.

OBJECTIVES

The effects of exposure to low-doses of DEHP on the continually growing incisors were analyzed in mouse males and females.

METHODS

Adult male and female C57BL/6J mice were exposed daily to 0.5, 5, and 50μg/kg per day DEHP for 12 wk and their incisors clinically examined. Incisors of males were further analyzed by scanning electron microscopy (SEM), micro X-ray computed tomography (micro-computed tomography; μCT), and nanoindentation for the enamel, histology and real-time quantitative polymerase chain reaction (RT-qPCR) for the dental epithelium.

RESULTS

Clinical macroscopic observations of incisors showed various dose-dependent dental lesions such as opacities, scratches, and enamel breakdown in 30.5% of males (10 of 34 total incisors across three independent experiments), and 15.6% of females (7 of 46 incisors) at the highest dose, among which 18.1% (6 of 34 total incisors across three independent experiments) and 8.9% (4 of 46 incisors), respectively, had broken incisors. SEM showed an altered enamel surface and ultrastructure in DEHP-exposed male mice. Further characterization of the enamel defects in males by μCT showed a lower mineral density than controls, and nanoindentation showed a lower enamel hardness during all stages of enamel mineralization, with more pronounced alterations in the external part of the enamel. A delay in enamel mineralization was shown by several approaches (μCT, histology, and RT-qPCR).

DISCUSSION

We conclude that DEHP disrupted enamel development in mice by directly acting on dental cells with higher prevalence and severity in males than in females. The time window of DEHP effects on mouse tooth development led to typical alterations of structural, biochemical, and mechanical properties of enamel comparable to other EDCs, such as bisphenol A. The future characterization of dental defects in humans and animals due to environmental toxicants might be helpful in proposing them as early markers of exposure to such molecules. https://doi.org/10.1289/EHP10208.

Bioremediation of lignin derivatives and phenolics in wastewater with lignin modifying enzymes: Status, opportunities and challenges

Lignin modifying enzymes from fungi and bacteria are potential biocatalysts for sustainable mitigation of different potentially toxic pollutants in wastewater. Notably, the paper and pulp industry generates enormous amounts of wastewater containing high amounts of complex lignin-derived chlorinated phenolics and sulfonated pollutants. The presence of these compounds in wastewater is a critical issue from environmental and toxicological perspectives. Some chloro-phenols are harmful to the environment and human health, as they exert carcinogenic, mutagenic, cytotoxic, and endocrine-disrupting effects. In order to address these most urgent concerns, the use of oxidative lignin modifying enzymes for bioremediation has come into focus. These enzymes catalyze modification of phenolic and non-phenolic lignin-derived substances, and include laccase and a range of peroxidases, specifically lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), and dye-decolorizing peroxidase (DyP). In this review, we explore the key pollutant-generating steps in paper and pulp processing, summarize the most recently reported toxicological effects of industrial lignin-derived phenolic compounds, especially chlorinated phenolic pollutants, and outline bioremediation approaches for pollutant mitigation in wastewater from this industry, emphasizing the oxidative catalytic potential of oxidative lignin modifying enzymes in this regard. We highlight other emerging biotechnical approaches, including phytobioremediation, bioaugmentation, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based technology, protein engineering, and degradation pathways prediction, that are currently gathering momentum for the mitigation of wastewater pollutants. Finally, we address current research needs and options for maximizing sustainable biobased and biocatalytic degradation of toxic industrial wastewater pollutants.

Exposure to persistent organic pollutants during tooth formation: molecular mechanisms and clinical findings

Persistent organic pollutants (POPs) constitute a relevant part of environmental pollution. POPs are chemical compounds that persist for a long time in the environment, bio-accumulate in the human body and determine significant adverse consequences to human health. The characteristics of these substances are lipo-affinity, semi-volatility and resistance to the degradation processes. Results deriving from several different studies attest that exposure to the main classes of POPs results in multiple toxic effects on humans and experimental animal models. Among the various alterations caused by exposition to and bio-accumulation of POPs, there are abnormalities in tooth formation and related hard dental tissue structure, especially enamel. This review aimed to describe the close association between the exposure of these compounds during the development of the tooth germ and the occurrence of tooth structural anomalies. Indeed, structural defects of the enamel have as possible consequences higher susceptibility of the tooth to caries disease and higher fragility of the crown to the occlusal trauma.

[Oral cavity as a target and a marker of environmental exposures: developmental dental defects]

The oral cavity is one of the main route for environmental contaminations associated to many chronic diseases (cancers, fertility and behavior disorders for example) via alimentation, medications and respiration. These environmental factors including, among others, endocrine disruptors and excessive fluoride can disrupt dental development and thus generate irreversible enamel defects. These defects are then treated with materials that may release molecules capable of generating these defects, leading to a vicious circle, particularly in pregnant women and young children. The present paper aims to review the state of knowledge, questions and controversies on common environmental factors in contact with the oral cavity. It also reviews their mechanisms of action and the mediators involved in enamel pathologies associated with environmental conditions. Dental tissues can not only be targeted by environmental factors but can also serve as early and easily accessible markers of exposure to these agents. Understanding and characterizing the environmental impact in the oral cavity will help to prevent multiple diseases, oral and distant, whose link with oral homeostasis is just being explored.

Persistent Threats by Persistent Pollutants: Chemical Nature, Concerns and Future Policy Regarding PCBs-What Are We Heading For?

Polychlorinated biphenyl (PCB)-contaminated sites around the world affect human health for many years, showing long latency periods of health effects. The impact of the different PCB congeners on human health should not be underestimated, as they are ubiquitous, stable molecules and reactive in biological tissues, leading to neurological, endocrine, genetic, and systemic adverse effects in the human body. Moreover, bioaccumulation of these compounds in fatty tissues of animals (e.g., fish and mammals) and in soils/sediments, results in chronic exposure to these substances. Efficient destruction methods are important to decontaminate polluted sites worldwide. This paper provides an in-depth overview of (i) the history and accidents with PCBs in the 20th century, (ii) the mechanisms that are responsible for the hazardous effects of PCBs, and (iii) the current policy regarding PCB control and decontamination. Contemporary impacts on human health of historical incidents are discussed next to an up to date overview of the health effects caused by PCBs and their mechanisms. Methods to decontaminate sites are reviewed. Steps which lead to a policy of banning the production and distribution of PCBs are overviewed in a context of preventing future accidents and harm to the environment and human health.

Expression of Steroid Receptors in Ameloblasts during Amelogenesis in Rat Incisors

Endocrine disrupting chemicals (EDCs) play a part in the modern burst of diseases and interfere with the steroid hormone axis. Bisphenol A (BPA), one of the most active and widely used EDCs, affects ameloblast functions, leading to an enamel hypomineralization pattern similar to that of Molar Incisor Hypomineralization (MIH). In order to explore the molecular pathways stimulated by BPA during amelogenesis, we thoroughly investigated the receptors known to directly or indirectly mediate the effects of BPA. The expression patterns of high affinity BPA receptors (ERRγ, GPR30), of ketosteroid receptors (ERs, AR, PGR, GR, MR), of the retinoid receptor RXRα, and PPARγ were established using RT-qPCR analysis of RNAs extracted from microdissected enamel organ of adult rats. Their expression was dependent on the stage of ameloblast differentiation, except that of ERβ and PPARγ which remained undetectable. An additional large scale microarray analysis revealed three main groups of receptors according to their level of expression in maturation-stage ameloblasts. The expression level of RXRα was the highest, similar to the vitamin D receptor (VDR), whereas the others were 13 to 612-fold lower, with AR and GR being intermediate. Immunofluorescent analysis of VDR, ERα and AR confirmed their presence mainly in maturation- stage ameloblasts. These data provide further evidence that ameloblasts express a specific combination of hormonal receptors depending on their developmental stage. This study represents the first step toward understanding dental endocrinology as well as some of the effects of EDCs on the pathophysiology of amelogenesis.

Polychlorinated biphenyls: New evidence from the last decade

Millions of pounds of polychlorinated biphenyl (PCB) compounds have been produced in multiple countries for industrial applications over the last several decades. PCB exposure induces various adverse health effects in animals and humans. Environmental and occupational exposures to PCBs have been associated with liver, kidney, endocrine, and neurodevelopmental adverse effects. We have collected and reviewed animal and human data cited in the US National Library of Medicine from 2000 to 2010. In brief, our review shows new evidence, that is, in animal studies, exposure to one of the PCBs, A1221, induces a significant alteration of serum luteinizing hormone. The effects were more profound in the F2 generation, particularly with respect to fluctuations in hormones and reproductive tract tissues across the estrous cycle. Morphological analyses of brain tissue from rats exposed to A1254 confirmed the results of an earlier work which showed that the relative size of the intra- and infrapyramidal (II-P) mossy fibers was smaller than that in the controls and also reduction in growth was selective for the II-P mossy fibers. PCB exposure increased anogenital distance and prostate size but decreased epididymal weight, epididymal sperm count, and motile epididymal sperm count. No effects were observed on testicular weight or size. The epidemiological data showed an association between diabetes mellitus prevalence and elevated concentrations of PCB 153. Additionally, prenatal PCB exposure studies were associated with a smaller thymic index at birth and could adversely affect immune responses to childhood vaccinations and resistance to respiratory infections. PCB exposure was also reported to adversely affect enamel development in children in a dose-dependent manner. Because PCBs and their metabolites are potential health hazards, understanding the risk factors associated with individual PCBs, PCB mixtures, and PCB metabolites is important. PCB exposures of vulnerable populations (pregnant women, fetuses, infants, and children) are of particular concern because of heightened sensitivity during this period of brain development.

Androgen Receptor Involvement in Rat Amelogenesis: An Additional Way for Endocrine-Disrupting Chemicals to Affect Enamel Synthesis

Endocrine-disrupting chemicals (EDCs) that interfere with the steroid axis can affect amelogenesis, leading to enamel hypomineralization similar to that of molar incisor hypomineralization, a recently described enamel disease. We investigated the sex steroid receptors that may mediate the effects of EDCs during rat amelogenesis. The expression of androgen receptor (AR), estrogen receptor (ER)-α, and progesterone receptor was dependent on the stage of ameloblast differentiation, whereas ERβ remained undetectable. AR was the only receptor selectively expressed in ameloblasts involved in final enamel mineralization. AR nuclear translocation and induction of androgen-responsive element-containing promoter activity upon T treatment, demonstrated ameloblast responsiveness to androgens. T regulated the expression of genes involved in enamel mineralization such as KLK4, amelotin, SLC26A4, and SLC5A8 but not the expression of genes encoding matrix proteins, which determine enamel thickness. Vinclozolin and to a lesser extent bisphenol A, two antiandrogenic EDCs that cause enamel defects, counteracted the actions of T. In conclusion, we show, for the first time, the following: 1) ameloblasts express AR; 2) the androgen signaling pathway is involved in the enamel mineralization process; and 3) EDCs with antiandrogenic effects inhibit AR activity and preferentially affect amelogenesis in male rats. Their action, through the AR pathway, may specifically and irreversibly affect enamel, potentially leading to the use of dental defects as a biomarker of exposure to environmental pollutants. These results are consistent with the steroid hormones affecting ameloblasts, raising the issue of the hormonal influence on amelogenesis and possible sexual dimorphism in enamel quality.

Family-Based Genetic Association for Molar-Incisor Hypomineralization

Despite some evidence of genetic and environmental factors on molar-incisor hypomineralization (MIH), its aetiology remains unclear. This family-based genetic association study aimed more comprehensively to investigate the genetic carriage potentially involved in MIH development. DNA was obtained from buccal cells of 391 individuals who were birth family members of 101 Brazilian nuclear families. Sixty-three single nucleotide polymorphisms (SNPs) were investigated in 21 candidate genes related to amelogenesis using the TaqMan™ OpenArray™ Genotyping platform. All SNPs were genotyped in 165 birth family members unaffected by MIH, 96 with unknown MIH status and 130 affected individuals (50.7% with severe MIH). Association analysis was performed by the transmission/disequilibrium test (TDT), and statistical results were corrected using the false discovery rate. Significant results were obtained for SNPs rs7821494 (FAM83H gene, OR = 3.7; 95% CI = 1.75-7.78), rs34367704 (AMBN gene, OR = 2.7; 95% CI = 1.16-6.58), rs3789334 (BMP2 gene, OR = 2.9; 95% CI = 1.34-6.35), rs6099486 (BMP7 gene, OR = 2.2; 95% CI = 1.14-4.38), rs762642 (BMP4 gene, OR = 2.3; 95% CI = 1.38-3.65), rs7664896 (ENAM gene, OR = 2.1; 95% CI = 1.19-3.51), rs1711399 (MMP20 gene, OR = 0.4; 95% CI = 0.20-0.72), rs1711423 (MMP20 gene, OR = 2.1; 95% CI = 1.18-3.61), rs2278163 (DLX3 gene, OR = 2.8; 95% CI = 1.26-6.41), rs6996321 (FGFR1 gene, OR = 2.7; 95% CI = 1.20-5.88), and rs5979395 (AMELX gene, OR = 11.7; 95% CI = 1.63-84.74). Through this family-based association study, we concluded that variations in genes related to amelogenesis were associated with the susceptibility to develop MIH. This result is in agreement with the multifactorial idea of the MIH aetiology, but further studies are necessary to investigate more thoroughly the factors that could influence MIH.

Was molar incisor hypomineralisation (MIH) present in archaeological case series?

OBJECTIVE

With respect to the unknown aetiology of molar incisor hypomineralisation (MIH), it is unclear whether this phenomenon was overlooked in the last century as a result of a high number of caries in children or if this developmental disorder was not present until then. Therefore, this study determined the presence of MIH in historical dentitions and teeth.

MATERIALS AND METHODS

Dental remains from late medieval (n = 191, twelfth-sixteenth century, Regensburg, Germany), post-medieval (n = 33, sixteenth-eighteenth century, Passau, Germany) and modern age archaeological skeletal series (n = 99, nineteenth-twentieth century, Altdorf, Germany) were examined for MIH. In addition, linear enamel hypoplasia (LEH), diffuse opacities, hypoplasia and Turner's teeth were documented.

RESULTS

MIH-related demarcated opacities or enamel breakdowns were found in only 15 (0.4 %) of the 3891 examined permanent teeth. Ten cases (3.1 %) from a total of 323 dentitions were classified as having MIH. In contrast, 98 individuals (30.3 %) showed LEH. Other enamel disorders were recorded in 64 individuals (19.8 %).

CONCLUSION

With respect to the low number of affected dentitions and teeth, MIH most likely did not exist or was at least rarely present in the investigated archaeological case series.

CLINICAL RELEVANCE

This study supports the hypothesis that MIH may be linked to contemporary living conditions or other health-related factors.

Simple reaction time in 8-9-year old children environmentally exposed to PCBs

Simple reaction time (SRT) has been studied in children exposed to polychlorinated biphenyls (PCBs), with variable results. In the current work we examined SRT in 146 boys and 161 girls, aged 8.53 ± 0.65 years (mean ± SD), exposed to PCBs in the environment of eastern Slovakia. We divided the children into tertiles with regard to increasing PCB serum concentration. The mean ± SEM serum concentration of the sum of 15 PCB congeners was 191.15 ± 5.39, 419.23 ± 8.47, and 1315.12 ± 92.57 ng/g lipids in children of the first, second, and third tertiles, respectively. We created probability distribution plots for each child from their multiple trials of the SRT testing. We fitted response time distributions from all valid trials with the ex-Gaussian function, a convolution of a normal and an additional exponential function, providing estimates of three independent parameters μ, σ, and τ. μ is the mean of the normal component, σ is the standard deviation of the normal component, and τ is the mean of the exponential component. Group response time distributions were calculated using the Vincent averaging technique. A Q-Q plot comparing probability distribution of the first vs. third tertile indicated that deviation of the quantiles of the latter tertile from those of the former begins at the 40th percentile and does not show a positive acceleration. This was confirmed in comparison of the ex-Gaussian parameters of these two tertiles adjusted for sex, age, Raven IQ of the child, mother's and father's education, behavior at home and school, and BMI: the results showed that the parameters μ and τ significantly (p ≤ 0.05) increased with PCB exposure. Similar increases of the ex-Gaussian parameter τ in children suffering from ADHD have been previously reported and interpreted as intermittent attentional lapses, but were not seen in our cohort. Our study has confirmed that environmental exposure of children to PCBs is associated with prolongation of simple reaction time reflecting impairment of cognitive functions.

Association of characteristics of delivery and medical conditions during the first month of life with developmental defects of enamel

Background

Developmental defects of enamel (DDE) may be influenced by health problems and illness in children. The aim of the study was to identify the main characteristics of birth (delivery) and adverse medical conditions during the first month of life that may be related to DDE in permanent teeth.

Methods

1000 schoolchildren between the ages of 9 and 11 years were selected for this cross-sectional study by multistage randomization from four educational zones in Shiraz in 2013. Intraoral examination was used to diagnose DDE according to World Health Organization screening guidelines and the Modified DDE Index. The data on seven birth factors as well as health and nutritional conditions during the first month of life were collected by a questionnaire completed by the parents, and were analyzed with the chi-squared test, Spearman’s correlation and binary logistic regression.

Results

469 (48.2%) out of 974 schoolchildren had at least one permanent tooth with DDE. The defects were significantly related with Apgar score at birth <7 (p = 0.003) and illness during the first month (p = 0.035). The frequency of DDE was significantly lower in the third child in families compared to the first and second child (p = 0.005). However, DDE showed no significant relationship with gestational age, delivery type, birth weight, gender or type of feeding during early infancy.

Conclusions

Three associated factors were identified (birth Apgar score, illness during the first month of life, birth order) for DDE in permanent teeth. No specific illness was found to be significantly associated with DDE.

Levels and distribution of organochlorine pollutants in primary dental tissues and bone of lamb

This study examined the bioconcentration of selected organochlorine pollutants, tetra- and hexa-chlorobiphenyls with planar (PCB-80, PCB-169) and non-planar (PCB-54, PCB-155) structure, and persistent organochlorine pesticides with planar [hexachlorobenzene (HCB)] and non-planar [1,1-bis (4-chlorophenyl)-2,2-dichloroethene (4,4'-DDE)] structure in primary dental tissues (pulp, dentine, and enamel) and mandibular bone of lactationally exposed lambs, and compared it with the organochlorines distribution pattern in permanent dental tissues and bone. Also, the role of pollutants physicochemical properties and tissue specific characteristics in the bioconcentration was assessed. Residual levels of individual pollutants were analyzed by high-resolution gas chromatography with electron-capture detection. Our results showed that transfer of organochlorines to primary hard dental tissues was higher than to permanent hard dental tissues. Metabolically more stable, planar, and toxic organochlorines (e.g. PCB-169 and HCB) predominated in primary hard dental tissues, where they may represent a potential risk for developmental dental defects.

Molar incisor hypomineralisation: possible aetiological factors in children from urban and rural areas

AIM

To analyse factors potentially associated with molar incisor hypomineralisation (MIH) development. METH¬ODS: A population-based study was carried out with 903 children aged from 6-12 years old, born and residing in rural and urban areas of the town of Botelhos, State of Minas Gerais, Brazil. Their mothers completed a structured medical history questionnaire, from pregnancy to the child's 3rd year of life. Two examiners evaluated children for MIH according to criteria suggested by the European Academy of Paediatric Dentistry. Descriptive analyses of the data and odds ratios (OR) with 95% test-based confidence intervals (CI) were estimated. Chi-square test was used to evaluate the differences between groups.

RESULTS

The prevalence of MIH in children from rural area (RA) was significantly higher than those from the urban area (UA) (24.9% versus 17.8%, p= 0.01). In urban children, neither significant associations with MIH nor medical problems were found. In rural children, however, MIH was significantly more common among those whose mothers had experienced medical problems during pregnancy (OR=2.11; 1.01-4.37 CI 95%; p=0.04), who had throat infections (OR=2.93; 1.47-5.87 CI 95%; p=0.01), who had high fever (OR=1.91; 1.07-3.39 CI 95%; p=0.02), and who had used amoxicillin associated with other antibiotics (OR=1.92; 1.02-3.62 CI 95%; p=0.04) during the first 3 years of life.

CONCLUSION

This study suggests a link between MIH and health problems during pregnancy, as well as environmental factors.

Essentiality of early diagnosis of molar incisor hypomineralization in children and review of its clinical presentation, etiology and management

Molar incisor hypomineralization (MIH) is a common developmental condition resulting in enamel defects in first permanent molars and permanent incisors. It presents at eruption of these teeth. One to four molars, and often also the incisors, could be affected. Since first recognized, the condition has been puzzling and interpreted as a distinct phenomenon unlike other enamel disturbances. Early diagnosis is essential since, rapid breakdown of tooth structure may occur, giving rise to acute symptoms and complicated treatment. The purpose of this article is to review MIH and illustrate its diagnosis and clinical management in young children. How to cite this article: Garg N, Jain AK, Saha S, Singh J. Essentiality of Early Diagnosis of Molar Incisor Hypomineralization in Children and Review of its Clinical Presentation, Etiology and Management. Int J Clin Pediatr Dent 2012;5(3):190-196.

A biobank of primary teeth within the Norwegian Mother and Child Cohort Study (MoBa): a resource for the future

The Norwegian Mother and Child Cohort Study (MoBa) is a prospective population-based cohort study including >100 000 pregnancies and following the children through childhood, using questionnaires and collecting biological samples. The aim of MoBa is to test specific aetiological hypotheses by estimating the association between exposure and disease, aiming at prevention. A biobank for exfoliated primary teeth collected from the children participating in MoBa has been established (MoBaTooth Biobank). Samples of tooth tissues from the primary dentition can give information about exposure to toxic and essential elements during fetal life and early infancy. Prenatally and postnatally formed tooth tissues permanently document early exposures unlike other biomarkers, as teeth form incrementally at a known rate. Results from tooth analyses will be coupled with corresponding information in the multiple questionnaires and data from analysis of other biological samples collected by MoBa. Invitations to donate one or more teeth are sent to all mothers/children in the period 2008-2016, when the child is 6.75 years old. By August 2011, 7400 participants had been recorded into the MoBaTooth database donating altogether 9798 teeth (1.3 teeth per child). The response rate was 24%, but there is a lag of >1 year in the response. Data from the tooth biobank can supply MoBa with important additional information on the uptake of trace elements during fetal life and early infancy. This information can illuminate possible causal factors of health and disease in the future.

Analysis of the toxicogenomic effects of exposure to persistent organic pollutants (POPs) in Slovakian girls: correlations between gene expression and disease risk

The chemical composition of persistent organic pollutants (POPs) in the environment is not uniform throughout the world, and these contaminants contain many structurally different lipophilic compounds. In a well-defined study cohort in the Slovak Republic, the POP chemicals present in the peripheral blood of exposed children were chemically analyzed. The chemical analysis data revealed that the relative concentration and profile of structurally different organic pollutants, including polychlorinated biphenyls (PCBs), 2,2'-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), 2,2'-bis(4-chlorophenyl)-1,1,1-trichloro-ethane (p,p'-DDT), hexachlorobenzene (HCB) and β-hexachlorocyclohexane (β-HCH), may vary from individual to individual, even within the same exposure area. These chemicals can be broadly classified into two groups. The first group, the PCB congeners, primarily originated from industrial compounds and their byproducts. The second group of compounds originated from or was commonly used in the agricultural sector (e.g., DDT, HCB). The objective of this study was to examine the effects of the two POP exposure profiles on gene expression. For the study population, we selected pre-pubertal girls (mean age of 46.2±1.4 months) with high POP concentrations in their blood (>75% tile of total POP) and classified them in the high 'PCB' group when the total PCB concentration was significantly higher than the total concentration of other POP components and in the 'Other Than PCB' (OTP) group, when the total PCB concentration was significantly lower than the concentration of the other major POP constituents. A matched control group of girls (<25% tile of total POP) was selected for comparison purpose (n=5 per group). Our aims were to determine whether there were any common effects of high POP exposure at a toxicogenomic level and to investigate how exposure may affect physiological functions of the children in two different exposure scenarios. Global gene expression analysis using a microarray (Affymetrix Gene Chip Human genome U133 Plus 2.0 Array) platform was conducted on the total RNA of peripheral blood mononuclear cells from the girls. The results were analyzed by Partek GS, Louis, MI, which identified twelve genes (ATAD2B, BIVM, CD96, CXorf39, CYTH1 ETNK1, FAM13A, HIRA, INO80B, ODG1, RAD23B, and TSGA14) and two unidentified probe sets, as regulated differentially in both the PCB and OTP groups against the control group. The qRT-PCR method was used to validate the microarray results. The Ingenuity Pathway Analysis (IPA) software package identified the possible molecular impairments and disease risks associated with each gene set. Connective tissue disorders, genetic disorders, skeletal muscular disorders and neurological diseases were associated with the 12 common genes. The data therefore identified the potential molecular effects of POP exposure on a genomic level. This report underscores the importance of further study to validate the results in a random population and to evaluate the use of the identified genes as biomarkers for POP exposure.

Perception of molar-incisor hypomineralisation (MIH) by Iraqi dental academics

BACKGROUND

The understanding and detection of molar-incisor hypomineralisation (MIH) is linked to its recognition by clinicians. No study has investigated dental clinicians' level of perception regarding MIH in the Middle East region including Iraq.

AIM

To determine the perception of Iraqi academic clinicians about MIH prevalence, severity and aetiological factors.

DESIGN

A questionnaire, based on previous European and Australian/New Zealand studies was administered to the academic dental staff of Mosul University.

RESULTS

A response rate of 77.7% was reported. General dental practitioners represented 30.8% of the total respondents, whilst 65.1% were dentists with post-graduate qualification. The majority of the respondents (81.2%) encountered MIH in their clinical activities and 37.3% of them identified that the prevalence appeared to have increased in recent years. Fewer than half of the respondents observed MIH affected teeth on a monthly basis. The condition was less commonly seen in primary second molars than the first permanent molars. A variation in views was recorded about MIH specific aetiological factor/s. Respondents advocated the need for clinical training regarding MIH-aetiological and therapeutic fields.

CONCLUSIONS

Molar-incisor hypomineralisation is a condition commonly diagnosed by Iraqi dental academics. No apparent consensus existed between the general and specialist dentists regarding the anticipated prevalence, severity and aetiology of this condition.

Aetiology of Molar-Incisor Hypomineralisation: A systematic review

AIM

This was to review and assess the studies on aetiology of Molar-Incisor Hypomineralisation (MIH) or, as a proxy, of demarcated opacities in permanent first molars and to consider the potential factors involved with findings obtained in animal experiments.

METHODS

A systematic search by Medline online database was performed. Abstracts behind appropriate titles were studied and finally the full articles were evaluated for their strength of evidence in the aetiology of MIH.

RESULTS

From a total of 1,142 articles 28 were identified and selected for review. The selected papers covered medical problems in prenatal, perinatal and postnatal period, medication of the child during the first years of life, and exposure to fluoride or environmental toxicants (dioxins and PCBs) in the early childhood. Based on the assessment of the articles it was still not possible to specifically name those factors causing MIH although correlations between several potential factors and MIH were presented. Among the factors suggested and found to cause enamel defects in animal experiments were: high fever, hypoxia, hypocalcaemia, exposure to antibiotics (amoxicillin, a macrolide), and dioxins.

CONCLUSION

Despite increased knowledge on the aetiology of MIH insufficient evidence to verify the causative factors exists. Further studies, especially prospective ones, are needed to improve the level and strength of evidence of the role of the present putative factors and to reveal new factors that may be involved. Any combined effect of several factors should be taken into account. Experimental dose/response studies and research on the molecular mechanisms causing the abnormal function of the ameloblasts are also necessary to deepen our knowledge of MIH.

The impacts of organochlorines and other persistent pollutants on thyroid and metabolic health

High prevalence of thyroid and metabolic disorders has been repeatedly observed in the population living in the area of eastern Slovakia highly polluted by a mixture of PCBs, DDE and HCB since about 50 years ago. Among thyroid disorders, increase of thyroid volume as measured by ultrasound volumetry may be suggested as one of notable findings which appeared possibly related to increased OCs levels and to autoimmunity signs (e.g. positive thyroperoxidase antibodies in blood and/or hypoechogenicity image obtained by ultrasound), while some participation of individual susceptibility and also of immunogenic effect of OCs and iodine in this iodine replete country cannot be excluded. Another notable finding has been the increase of blood FT4 and TT3 positively related to high PCBs level. Such increased FT4 level has been found associated with TSH level in hyperthyroid range in about 2% of examined population from polluted area. High prevalence of thyroid autoimmune disorders strongly supported the assumption on impaired immune system and thus also on presumably increased prevalence of other autoimmune disorders in highly exposed population. In addition, markedly increased prevalence of prediabetes and diabetes significantly related to major OCs (PCBs, DDE and HCB) levels and accompanied by increasing level of cholesterol and triglycerides has been observed. The observations also suggested a role of prenatal exposure to OCs in the development of several adverse health signs (e.g. increased prevalence of thyroid antibodies, impaired fasting glucose level, increased thyroid volume, decreased thymus volume, decreased neurobehavioral performance, increased hearing and dental disorders) in young generation born to highly exposed mothers in polluted area.

High prevalence of prediabetes and diabetes in a population exposed to high levels of an organochlorine cocktail

AIMS/HYPOTHESIS

A heavily polluted area of Eastern Slovakia was targeted by the PCBRISK cross-sectional survey to search for possible links between environmental pollution and both prediabetes and diabetes.

METHODS

Associations of serum levels of five persistent organic pollutants (POPs), namely polychlorinated biphenyls (PCBs), 2,2'-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE), 2,2'-bis(4-chlorophenyl)-1,1,1-trichloro-ethane (p,p'-DDT), hexachlorobenzene (HCB) and beta-hexachlorocyclohexane (beta-HCH), with prediabetes and diabetes were investigated in 2,047 adults. Diabetes and prediabetes were diagnosed by fasting plasma glucose in all participants and by OGTT in 1,220 compliant participants.

RESULTS

Our population was stratified in terms of individual POPs quintiles and associations between environmental pollution, prediabetes and diabetes were investigated. Prevalence of prediabetes and diabetes increased in a dose-dependent manner, with individuals in upper quintiles of individual POPs showing striking increases in prevalence of prediabetes as shown by OR and 95% CI for PCBs (2.74; 1.92-3.90), DDE (1.86; 1.17-2.95), DDT (2.48; 1.77-3.48), HCB (1.86; 1.7-2.95) and beta-HCH (1.97; 1.28-3.04). Interestingly, unlike PCBs, DDT and DDE, increased levels of HCB and beta-HCH seemed not to be associated with increased prevalence of diabetes. Nevertheless, individuals in the 5th quintile of the variable expressing the cumulative effect of all five POPs (sum of orders) had a more than tripled prevalence of prediabetes and more than six times higher prevalence of diabetes when compared with the 1st referent quintile.

CONCLUSIONS/INTERPRETATION

Increasing serum concentrations of individual POPs considerably increased prevalence of prediabetes and diabetes in a dose-dependent manner. Interaction of industrial and agricultural pollutants in increasing prevalence of prediabetes or diabetes is likely.

Prevalence and distribution of demarcated opacities and their sequelae in permanent 1st molars and incisors in 7 to 13-year-old Brazilian children

OBJECTIVE

To determine the prevalence of demarcated opacities in permanent 1st molars and incisors in 7 to 13-year-old Brazilian children.

MATERIAL AND METHODS

The study population comprised 292 children from a middle social class public school in Rio de Janeiro, Brazil. Children with all 1st permanent molars erupted were eligible for participation. Clinical examination was performed by two calibrated examiners who recorded demarcated opacities, post-eruptive breakdown, atypical restorations, and extractions due to demarcated opacities. Forty-three children had at least one molar that could not be examined, which left 249 children for the data analysis.

RESULTS

One hundred children (40.2%) had one or more 1st molars with demarcated opacities with a mean number of 1.98 (SD 1.09) affected molars. The number of affected incisors increased with increasing number of affected molars. Twenty-two (18.6%) of 118 children with unaffected 1st molars had affected incisors. Demarcated opacities were the most frequent defect, and 1st molars and upper central incisors were the most frequently affected teeth. Among children with demarcated opacities in 1st molars, 20 (20%) had post-eruptive breakdown.

CONCLUSIONS

A high prevalence of demarcated opacities, possibly resulting in disintegration of the tooth crown, has been found in Brazilian children.

Molar-incisor-hypomineralisation and dioxins: new findings

AIM

According to our earlier study, molar-incisor-hypomineralisation (MIH) was associated with the exposure of a child via mother's milk to polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) in a group of Finnish children born in 1987. Since the levels of PCDD/Fs and PCBs in mother's milk/placenta have remarkably decreased, it was important to find out if an association still exists.

METHODS

The study group was composed of 167 mothers and their children. Placental samples from the mothers were collected in maternity hospitals in Helsinki and Oulu in 1995--1999 and concentrations of the 17 most toxic PCDD/PCDF and 36 PCB congeners were measured. After 7-10 years the children were examined for MIH and the mothers were interviewed on the duration of breast-feeding.

RESULTS

MIH was found in 24 children (14.4%). The duration of breast-feeding ranged from 0 to 30 months (mean=7.2+/-4.7). WHOPCDD/FTEQ ranged from 2.5 to 39.1 pg/g fat (mean=13.7+/-6.8) and WHOPCBTEQ from 0.7 to 9.8 pg/g fat (mean=2.7+/-1.4). The mean sum of PCDD/Fs was 196+/-105 pg/g fat and that of PCBs was 57.2+/-28.1ng/g fat. The total exposure to PCDD/Fs, which was calculated from the placental concentration (used as a proxy for the milk concentration) and duration of breastfeeding, was not associated with the occurrence or severity of MIH. Neither was the total exposure to PCBs associated with the occurrence or severity of MIH.

CONCLUSION

At prevailing levels, exposure of a child via placenta/mother's milk to PCDD/Fs and PCBs is not associated with MIH.

The prevalence of molar incisor hypomineralization (MIH) in a group of children in a highly polluted urban region and a windfarm-green energy island

BACKGROUND

Children's developing teeth may be sensitive to environmental pollutants such as polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans. The term molar incisor hypomineralization (MIH) was introduced to describe the clinical appearance of enamel hypomineralization of systemic origin affecting one or more permanent first molars (PFMs) that are associated frequently with affected incisors.

AIM

The aim of this study was to determine the prevalance of MIH in children from the most industrialized and polluted region and the most green-energy island of Turkey.

DESIGN

In September 2007, a retrospective study was initiated in two elementary schools: one, a group of children (N = 153) who fitted the criteria from Tavsancil, Kocaeli (N = 109) and the other from Bozcaada island, Canakkale (N = 44). The soil samples were collected from selected regions in order to determine the contamination levels in a heavily industrialized area and a non-industrialized area.

RESULTS

Prevalance of MIH in children in Bozcaada island was 9.1%, while prevalance of MIH was 9.2% in Tavsancil. The PCDD/F levels in soil samples collected from Bozcaada and Tavsancil were determined as 1,12 and 8,4 I-TEQ ng/kg dry soil, respectively (P < 0.001).

CONCLUSIONS

In this preliminary study with a small study population, prevalence of MIH did not seem to be associated with the levels of PCDD/Fs in the environment.

Aetiology of molar-incisor hypomineralization: a critical review

OBJECTIVE

The objective of this study was to assess the strength of evidence for the aetiology of molar-incisor hypomineralization (MIH), often as approximated by demarcated defects.

METHOD

A systematic search of online medical databases was conducted with assessment of titles, abstracts, and finally full articles for selection purposes. The level and quality of evidence were then assessed for each article according to Australian national guidelines.

RESULTS

Of 1123 articles identified by the database search, 53 were selected for review. These covered a variety of potential aetiological factors, some of which were grouped together for convenience. The level of evidence provided by the majority of papers was low and most did not specifically investigate MIH. There was moderate evidence that polychlorinated biphenyl/dioxin exposure is involved in the aetiology of MIH; weak evidence for the role of nutrition, birth and neonatal factors, and acute or chronic childhood illness/treatment; and very weak evidence to implicate fluoride or breastfeeding.

CONCLUSION

There is currently insufficient evidence in the literature to establish aetiological factor/s relevant for MIH. Improvements in study design, as well as standardization of diagnostic and examination protocols, would improve the level and strength of evidence.

Exposure to polychlorinated biphenyls and hearing impairment in children

The objective of this cross-sectional epidemiological study was to assess if long-term exposure to polychlorinated biphenyls (PCBs) is associated with hearing impairment. Four hundred and thirty-three children aged 8-9 years residing in an area polluted by PCBs in Eastern Slovakia were examined otoscopically, tympanometrically and by pure tone audiometry. PCB levels in their serum were determined by gas chromatography. Transient otoacoustic emissions (TEOAE) were measured in a subgroup of 161 children. The mean of the sum of PCB concentrations in serum was 528.2ng/g serum lipids (median 321ng/g serum lipids). Serum PCB concentrations were associated with an increase of hearing threshold at low frequencies and a negative correlation between serum PCBs and the amplitude of TEOAE response was observed in the uppermost tertile of children grouped with regard to serum PCBs, not related to thyroid hormone levels. It was concluded that long-term environmental exposure to PCBs is associated with subclinical but diagnosable hearing deficits.

Dental caries in Faroese children exposed to polychlorinated biphenyls

The effects of exposure to polychlorinated biphenyls (PCBs) on dental caries of first permanent molars in children in the Faroe Islands, where the population is exposed to PCBs in their traditional diet, were evaluated. This study was part of a cohort study aimed at determining developmental risks resulting from the consumption of contaminated seafood. One hundred and fourteen children from a birth cohort of 182 mother-child pairs, aged 9-10 years, were examined. Caries scoring was performed according to WHO criteria; cavitated and noncavitated lesions were included. Exposure assessment was based on the PCB concentrations in maternal milk samples. Data from the project data set provided information on various confounding factors. Mean maternal milk PCB concentration was 2205 (range 70-11,150)ng/g lipids. The number of carious surfaces of first permanent molars correlated with milk PCB concentration (r=0.26, p=0.01). In multivariate linear regression analysis, PCB exposure was significantly related to caries susceptibility. The findings support an association between children's PCB exposure and caries prevalence.