The evaluation of zinc and copper content in tooth enamel without any pathological changes - an in vitro study

Correlation Between Urinary Heavy Metals and Early Childhood Caries in a Typical Industrial and Mining Area

In order to assess the association between urinary heavy metals and early childhood caries (ECC), a survey of deciduous tooth decay and urinary heavy metal concentrations of 408 children was conducted in a typical industrial and mining area. The results indicated that urinary heavy metal concentrations were ranked as Zn > Fe > Cu > Pb > Ni > Cd > As > Cr > Mn > Hg. The zero-inflated negative binomial model identified Hg as a significant risk factor for ECC (P25 ~ P75, OR = 3.499; > P75, OR = 3.184). Bayesian kernel machine regression further revealed that Pb, Cd, and Hg were positively correlated with ECC. Additional analysis using the Wilcoxon rank sum test and restricted cubic splines confirmed a positive correlation between the urinary concentrations of Pb, Cd, As, and Hg and the number of ECC (p < 0.05). Moreover, Bayesian kernel function regression and weighted quantile sum regression indicated that combined exposure to heavy metals was positively associated with ECC, with Hg (0.420) being the most dominant contributor, followed by As, Pb, and Cd. In conclusion, this study demonstrated a significant positive correlation between urinary heavy metals and both the occurrence and severity of ECC, with Hg identified as the most influential factor. It was recommended to minimize children's exposure to heavy metals to protect their dental health.

Content of cariostatic trace elements (F, Cu, and Zn) in the commercially packaged and public tap waters of Qatar

Objectives

Drinking water containing optimal levels of cariostatic trace elements is an effective preventive approach against community-wide dental caries. This study aimed to (i) determine the concentrations of fluoride, copper, and zinc in commercially packaged and public tap water available in Qatar, (ii) assess the accuracy of the content of these cariostatic trace elements on commercial water brand labels, and (iii) check for seasonal fluctuations in the levels of these trace elements in commercial and public water samples.

Methods

Duplicate samples from 20 commercial and six public tap water sources were collected once in the summer and winter seasons. Water samples were evaluated for fluoride concentration using ion chromatography (IC), whereas copper and zinc concentrations were estimated using inductively coupled plasma mass spectrometry (ICP-MS).

Results

The fluoride content of all commercial and public water samples was below the 0.25 mg/L detection limit of the IC instrument. Commercial water brands had copper and zinc levels below the ICP-MS detection limits (1.22 μg/L for copper and 0.24 μg/L for zinc). Copper levels in the public water samples ranged from <1.22 μg/L to 11 μg/L. Zinc levels in the public water samples ranged from 5 μg/L to 40 μg/L. Thirteen commercial water brands labelled their fluoride content, with most showing labelled fluoride levels <0.1 mg/L, consistent with the results of this study. The difference in trace element content between the summer and winter water samples was not statistically significant (P > 0.05).

Conclusions

Lower optimal cariostatic trace element content in the drinking water in Qatar could be a reason for the exceptionally high prevalence of dental caries. The results of this study could lead to public health advocacy for supplementing drinking water in Qatar with cariostatic trace elements that could potentially lower the prevalence of dental caries.

The Distribution and Biogenic Origins of Zinc in the Mineralised Tooth Tissues of Modern and Fossil Hominoids: Implications for Life History, Diet and Taphonomy

Zinc is incorporated into enamel, dentine and cementum during tooth growth. This work aimed to distinguish between the processes underlying Zn incorporation and Zn distribution. These include different mineralisation processes, the physiological events around birth, Zn ingestion with diet, exposure to the oral environment during life and diagenetic changes to fossil teeth post-mortem. Synchrotron X-ray Fluorescence (SXRF) was used to map zinc distribution across longitudinal polished ground sections of both deciduous and permanent modern human, great ape and fossil hominoid teeth. Higher resolution fluorescence intensity maps were used to image Zn in surface enamel, secondary dentine and cementum, and at the neonatal line (NNL) and enamel-dentine-junction (EDJ) in deciduous teeth. Secondary dentine was consistently Zn-rich, but the highest concentrations of Zn (range 197-1743 ppm) were found in cuspal, mid-lateral and cervical surface enamel and were similar in unerupted teeth never exposed to the oral environment. Zinc was identified at the NNL and EDJ in both modern and fossil deciduous teeth. In fossil specimens, diagenetic changes were identified in various trace element distributions but only demineralisation appeared to markedly alter Zn distribution. Zinc appears to be tenacious and stable in fossil tooth tissues, especially in enamel, over millions of years.

Use of zinc deposited in deciduous teeth as a retrospective measurement of dietary zinc exposure during early development

Purpose

We proposed that zinc (Zn) deposition in deciduous teeth would be a timed record of exposure to this essential micronutrient over very early life. We tested this hypothesis by gathering information on the maternal and child's diet during pregnancy and early infancy and measuring mineral deposition in the dentine at points during deciduous tooth development.

Methods

We developed a short food frequency questionnaire (S-FFQ) to record consumption of food containing Zn during pregnancy and over the first year of life of the child in an Indonesian population. Zn, Sr and Ca were measured by laser ablation ICP-MS in a series of points across the developmental timeline in deciduous teeth extracted from 18 children undergoing the process as part of dental treatment whose mothers completed the SFFQ. Mothers and children were classified into either high Zn or low Zn groups according to calculated daily Zn intake.

Results

The Zn/Sr ratio in dentine deposited over late pregnancy and 0-3 months post-partum was higher (p < 0.001, 2-way ANOVA; p < 0.05 by Holm-Sidak post hoc test) in the teeth of children of mothers classified as high Zn consumers (n = 10) than in children of mothers classified as low Zn consumers (n = 8).

Conclusion

The S-FFQ was validated internally as adequately accurate to measure zinc intake retrospectively during pregnancy and post-partum (∼7 years prior) by virtue of the correlation with measurements of zinc in deciduous teeth. The ratio of Zn/Sr in deciduous teeth appears to be a biomarker of exposure to zinc nutrition during early development and offers promise for use as a record of prior exposure along a timeline for research studies and, potentially, to identify individuals at heightened risk of detrimental impacts of poor early life zinc nutrition on health in later life and to implement preventative interventions.

NUTRITION AND MINERAL CONTENT IN HUMAN TEETH THROUGH THE CENTURIES

OBJECTIVES

The objectives of the study were: (i) to compare mineral values of calcium, phosphorus, magnesium, zinc and their ratios, in teeth from Croatian populations that lived in different historical periods, namely the Medieval period, the early 20th century, and the 21 st century; and (ii) to elucidate the influence of diet and lifestyle on tooth quality in these groups.

DESIGN

Determination of mineral content (Ca, Mg, P and Zn) in 294 teeth from three different periods of history (Medieval Period [G1], Second World War period [G2] and the contemporary period [G3]) using atomic absorption spectrometer and UV/VIS spectrometer methods.

RESULTS

Our results showed that the mineral content in teeth has changed over the centuries. Between analysed samples from all groups, there were significant differences in the elemental content as well as in the interrelationship of the elements. The largest differences were observed in the mean values of magnesium and zinc concentrations while smaller differences were observed for changes in calcium and phosphorus.

CONCLUSIONS

From the obtained results, it is evident that there are changes in the tooth mineral composition in specimens centuries apart that could be a reflection of changes in eating habits, food quality and the environment. In addition to differences in individual elements, differences in their mutual ratios were also observed.

Impact of copper on in-vitro biomineralization, drug release efficacy and antimicrobial properties of bioactive glasses

This study highlights the incorporation of copper in the bioactive glasses (BAG) network that greatly influences the morphological, structural and biological properties. By increasing the copper incorporation in BAG, increment in cell volume was obtained from XRD patterns, and concomitantly, dominant phosphate bands and latent silica bands were observed by FT-IR and Raman spectroscopic results. The Cu addition also affected particle appearance to vary from spherical to cluster-like cubes in 1.5% and 2.5% copper-doped BAG. Due to the mesoporous network 1.5% and 2.5% copper-doped BAG showed enhanced release of anti-inflammatory drugs such as Acetaminophen (ACE) and Ibuprofen (IBU) in which, the drug release profiles showed best fit with kinetic models of First order, Korsmeyar-Peppas and Higuchi. Copper doping influences the lattice of BAG, as a result morphology and porosity varied, which regulates the ionic dissolution, hence, prompting bioactivity was perceived from 1.5% and 2.5% copper-doped bioactive glasses (Cu-BGs). Moreover, 2.5% Cu-BG and 1.5% Cu-BG showed highest rate of ROS detection, as well as improved antimicrobial activity. This study established that up to certain proportion of copper incorporation in BAG network, potentially enhances the biomineralization and turns the morphology towards minimal size with mesoporous nature. Due to the abundance in oral microbial exposure, copper amplifies the superior antimicrobial properties, and Cu-BGs act as a drug carrier to load ACE and IBU, which potentially up-regulate the healing properties in dental application.

Synchrotron X-ray fluorescence mapping of Ca, Sr and Zn at the neonatal line in human deciduous teeth reflects changing perinatal physiology

OBJECTIVES

Our first objective was to review the evidence describing the appearance and microstructure of the neonatal line in human deciduous teeth and to link this with known changes in neonatal physiology occurring at and around birth. A second objective was to explore ways to improve identification of the neonatal line by mapping the pre- and postnatal distribution of Ca, Sr and Zn in deciduous cuspal enamel and superimposing these maps onto transmitted light micrographs that included a clear true section of the neonatal line.

MATERIALS AND METHODS

We used synchrotron X-ray fluorescence to map elemental distributions in pre- and postnatal enamel and dentine. Two deciduous canines and 5 deciduous molars were scanned with an X-ray beam monochromatised to 17.0 keV at either 10.0, 2.5 or 1.0 μm resolution and 10 ms integration time.

RESULTS

Calcium maps distinguished enamel and dentine but did not clearly demarcate tissues formed pre- or postnatally. Strontium maps reflected presumed pre- and postnatal maternal serum levels and what are likely to be diet-dependent regions of Sr enrichment or depletion. Prenatal Zn maps, particularly for dentine, mirror elevated levels in the fetus and in colostrum during the first few days of life.

CONCLUSIONS

The neonatal line, enamel dentine junction and surface enamel were all Zn-rich. Within the neonatal line Zn may be associated with increased crystallinity but also with caries resistance, both of which have been reported previously. Elemental mapping may improve the identification of ambiguous NNLs and so be useful in forensic and archaeological studies.

The presence and response to Zn of ZnT family mRNAs in human dental pulp

Zinc (Zn) is distributed throughout the body and within cells by saturable processes mediated by the transport proteins of the ZnT (SLC30) and ZIP (SLC39) families. The two families function in opposite directions. ZnT transporters mediate cellular zinc efflux or intracellular sequestration. Zn is found in human tooth enamel and dentine at levels that have been related to environmental exposures, such as pollution, disease, and dietary intake. The mechanism by which Zn in the odontoblast is deposited in the hard tissue of the tooth, however, is unknown but is important in determining the physical properties, and hence resilience, of enamel and in the context of the use of tooth zinc level as a biomarker of exposure. We hypothesised that zinc efflux mediated by members of the ZnT family of 10 transporters is a key step in this process and is regulated by zinc availability through effects on mRNA levels. Thus, we determined the profile of ZnT transporter mRNA in a human active-secretory odontoblast-like cell model under conditions of high- and low-extracellular Zn concentration and determined if the same transporter mRNAs were present in human dental pulp. ZnT1, ZnT5 and ZnT9 mRNAs were detected by RT-PCR in both the secretory odontoblast cells and human dental pulp. ZnT2, ZnT3 and ZnT10 mRNAs were not detected, and ZnT4 mRNA was detected in secretory odontoblasts only, which may be indicative of a specialised zinc efflux function during the active secretory phase of tooth development. ZnT1 mRNA was significantly increased in response to extracellular Zn exposure (60 μM) after 24 h. The presence of Zn transporter mRNAs in secretory odontoblasts and dental pulp indicates that the corresponding transport proteins function to deposit zinc in the dental hard tissues. The responsiveness of ZnT1 in odontoblasts to zinc availability is concordant with this being a process that is regulated to maintain cellular Zn homeostasis and that is a mediator of the relationship between environmental Zn exposure and dental Zn deposition. These findings have likely relevance to human dental health through effects of Zn transporter expression level on the hard tissue properties.