Do the levels of selected metals differ significantly between the roots of carious and non-carious teeth?

Permanent and decidua dentition as chronological biomarkers of heavy metal contamination: A review of the forensic literature

STATEMENT OF PROBLEM

Contamination with heavy metals (HM) has great environmental consequences in the environment due to lack of biodegradation, in addition, accumulation in living beings causes defects in tissues and organs, deteriorating their function and inducing a wide spectrum of diseases. Human biomonitoring consists of the periodic measurement of a certain chemical substance or metabolite in a particular population, using matrices that can be acute or chronic. Teeth are chronic matrices that have great characteristics of resistance and chronological storage of information. This review aims to identify the mechanisms, spatial location, and affinity of HM within teeth, along with understanding its applicability as a chronological record matrix in the face of HM contamination.

MATERIAL AND METHODS

A systematic search review was performed using the PubMed/Medline, Web of Science, and Scopus metasearch engines, and the terms "teeth" OR "dental" OR "tooth" AND "heavy metals" were intersected. Complete articles are included in Spanish, English and Portuguese without time restrictions, involving studies in humans or in vitro; Letters to the editor, editorials and those that did not refer to information on the incorporation and relationship of HM with the teeth were excluded.

RESULTS

837 published articles were detected, 91 were adjusted to the search objective, and 6 were manually included. Teeth are structures with a great capacity for information retention in the face of HM contamination due to low physiological turnover and their long processes of marked formations by developmental biorhythm milestones such as the neonatal line (temporal reference indicator). The contamination mechanisms inside the tooth are linked to the affinity of hydroxyapatite for HM; this incorporation can be in the soft matrix during the apposition phase or as part of the chemical exchanges between hydroxyapatite and the elements of the environment.

CONCLUSION

The teeth present unique characteristics of great resistance and affinity for HM, as well as a chronological biomarker for human biomonitoring, so they can be used as means of expertise or evidence to confirm or rule out a fact of environmental characteristics in the legal field.

The Influence of Environmental Exposure to Heavy Metals on the Occurrence of Selected Elements in the Maxillary Bone

The elemental composition of the body's calcified tissues may reflect the environmental exposure of the population to heavy metals. The aim of the study was to assess whether the elemental composition of the maxillary bone from individuals belonging to a given population reflects the environmental exposure of this population to lead and cadmium. The research material consisted of cortical bone from the anterolateral walls of the maxilla collected from 126 patients during Caldwell-Luc maxillary sinus surgery on residents of two cities differing in terms of the lead and cadmium pollution of the natural environment. The content levels of lead, cadmium, iron, manganese, chromium, copper, and iron were determined by using atomic absorption spectrophotometry. The content levels of lead and cadmium in the samples of the maxillary bones of residents of Bielsko-Biala were 3.26 ± 2.42 µg/g and 0.74 ± 0.38 µg/g, respectively, whereas in the samples from the residents of Katowice, they were 7.66 ± 2.79 µg/g and 1.12 ± 0.08 µg/g, respectively. It was found that the lead and cadmium levels in the maxillary bone corresponded to the environmental exposure to these heavy metals in the place of residence, which was proven here via the example of the residents of two cities with different concentrations of these heavy metals in the air over long time periods. Additionally, higher content levels of essential metals such as manganese, chromium, copper, and iron are characteristic of the maxillary bone samples of residents of the area that is more polluted with heavy metals.

Protective Effect of Increased Zinc Supply against Oxidative Damage of Sublingual Gland in Chronic Exposure to Cadmium: Experimental Study on Rats

Cadmium is one of the main chemical pollutants found in the daily environment of developed countries. Cigarettes are a significant source of that metal, which makes it important in terms of oral cavity health. The aim of this study was to determine if increased supply of zinc in chronic exposure to cadmium might protect the sublingual gland structure against oxidative damage. The experiment took 12 months and was conducted on 72 adult male rats. They were randomized into 9 groups. Eight groups received cadmium in drinking water (as CdCl₂) at 5 or 50 mg Cd/dm³ and/or zinc (as ZnCl₂) at 30 or 60 mg Zn/dm³. The control group received regular water. In the sublingual gland of all animal groups, levels of oxidative parameters were measured. The oxidative stress index was calculated as a TOS/TAS ratio. Cadmium exposure at 5 mg and 50 mg Cd/dm³ induced oxidative stress in the sublingual glands of the rats. Cadmium reduced the TAS and GSH levels and increased LPO, H₂O₂, TOS, and OSI. In cadmium exposure conditions, increasing the supply of zinc by 79% or 151%, as compared to the standard dietary intake of this microelement, completely prevented the reduction of TAS and GSH levels and accumulation of LPO, H₂O₂, and TOS in the examined gland at both exposure levels to that metal. The outcome data confirm the protective effect of increased zinc intake on the sublingual gland tissue in chronic cadmium exposure.

Selected toxic and essential heavy metals in impacted teeth and the surrounding mandibular bones of people exposed to heavy metals in the environment

BACKGROUND

The elemental composition of bones and teeth can allow exposure to heavy metals in the environment to be estimated. The aim of this study was to determine whether impacted mandibular teeth and the surrounding bones can be used as biomonitoring media to assess exposure to heavy metals.

METHODS

The research materials were 67 impacted lower third molars and samples of the cortical bone removed when the wisdom teeth were surgically extracted. The samples were from people living in two areas with different environmental concentrations of heavy metals. The cadmium, chromium, copper, iron, lead, manganese, and zinc concentrations in the samples were determined by atomic absorption spectrometry with flame atomization.

RESULTS

The cadmium and lead concentrations in the impacted third molars and the bones surrounding the teeth were significantly higher for people living in the relatively polluted Ruda Slaska region than for people living in Bielsko-Biala region. Significantly higher chromium, copper, manganese, and zinc concentrations were found in the bones surrounding the impacted teeth from people living in Ruda Slaska than in the bones surrounding the impacted teeth from people living in Bielsko-Biala. The cadmium concentrations in impacted teeth and the surrounding bones were significantly positively correlated.

CONCLUSION

The results indicated that impacted mandibular teeth and the surrounding mandibular bones may reflect the exposure of people to cadmium and lead in the environment. This conclusion, however, must be verified in future research projects designed to exclude the possibility of additional dietary, occupational, and other types of exposure to heavy metals.

Metallic Burden of Deciduous Teeth and Childhood Behavioral Deficits

Attention Deficit/Hyperactivity Disorder (ADHD) affects 5%–8% of children in the U.S. (10% of males and 4% of females). The contributions of multiple metal exposures to the childhood behavioral deficits are unclear, although particular metals have been implicated through their neurotoxicity. The objective of this study was to test the hypothesis that the body burden of Mn is positively correlated with ADHD symptoms. We also investigated the putative roles of Ca, Fe, Pb, and Hg. We collected shed molars from 266 children (138 boys and 128 girls) who lost a tooth between 11 and 13 years of age. The molars were analyzed for metals using ICP-OES. The third grade teacher of each child completed the Teacher’s Disruptive Behavior Disorders Rating Scale (DBD) to produce a score for “Total Disruptive Behavior” and subscale scores for “Attention Deficit Hyperactivity Disorder”, Hyperactivity/Impulsivity, Inattention, and Oppositional/Defiant. The mean Mn, Fe, Pb and Ca concentrations found in teeth was 3.1 ± 2.9 µg/g, 11.4 ± 12.1 µg/g, 0.5 ± 0.7 µg/g, and 3.0 × 10⁵ ± 0.8 × 10⁵ µg/g, respectively. Hg was not detected. No significant association was found between Mn and behavioral deficits. Ca was significantly negatively associated, and Pb showed a significant positive association with Hyperactivity/Impulsivity, Inattention, and Oppositional/Defiant Disorders. These findings call into question the putative independent association of manganese exposure and behavioral deficits in children, when the balance of other metallic burden, particularly Ca and Pb burdens play significant roles.

Blood levels of the heavy metal, lead, and caries in children aged 24-72 months: NHANES III

Lead remains a significant pollutant. It has acute toxic and chronic effects on many tissues and accumulates in teeth and bones. The researchers for this study investigated the association of blood lead levels with the extent/severity of caries as measured by the number of decayed/filled teeth of children aged 24-72 months using data from NHANES III (the Third National Health and Nutrition Examination Survey), accounting for the excess zero caries in the analysis and using less than 2 µg/dl as the reference blood lead level (n = 3,127). Zero-inflated negative binomial regression models indicated unadjusted extent/severity mean ratios of 1.79, 1.88 and 1.94 for the number of decayed/filled teeth in children whose blood lead levels were 2-5, 5-10 and >10 µg/dl, respectively, compared with children having <2 µg/dl blood lead levels. The results did not attenuate when other variables were added to the model for the 5-10 and >10 µg/dl levels of exposure. The adjusted extent/severity mean ratios were 1.84, 2.14 and 1.91, respectively, for the categories. This study indicated a strong association of blood lead levels with increasing numbers of carious teeth in children aged 24-72 months. These findings support other studies in an innovative analysis handling cases of children with no caries. The findings may inform caries risk assessment.

Changes of concentrations of elements in deciduous teeth with age

The aim of this study was to describe the issue of changes in the concentration of some elements (Mn, Fe, Mg, Cu, K, Cr, Pb, Cd, and Ca) in the mineral composition of deciduous teeth and to answer the question whether there was a tendency to change the metal concentration, depending on children's age. Physiological replacement of deciduous teeth is preceded with the remodeling process occurring in the mineral structure. The elemental composition of deciduous teeth tissue during their natural loss is the result of these transformations. The subject of the study was deciduous teeth taken from the children (n = 45, aged 5-14 years), residing in southern Poland, obtained as a result of noninvasive physiological replacement. The concentration of metals in samples was determined over the atomic absorption spectroscopy method. The results of the research showed a statistically significant decrease in the concentration of the analyzed elements in deciduous teeth of older children compared to younger children. The total concentration of all metals studied against the Ca content, expressed as the value of the constant cationic equilibrium, did not change in a statistically significant manner, depending on the age of the children (p > 0.05).

Spatial distribution of manganese in enamel and coronal dentine of human primary teeth

Emerging evidence indicates that excessive exposure to manganese (Mn) during the prenatal period and early childhood may result in neurodevelopmental deficits. However, accurate exposure biomarkers are not well established, limiting our understanding of exposure-response relationships over these susceptible periods of development. Naturally shed deciduous teeth are potentially a useful biomarker of environmental exposure to Mn. However, the uptake and distribution of Mn in human teeth has not been studied in detail. Mn distribution was measured at high resolution (~20 μm) in eight human primary teeth using laser ablation-inductively coupled plasma-mass spectrometry. A bio-imaging methodology was applied to construct detailed elemental maps of three incisors, and bone meal (NIST SRM 1486) was used to validate the analyses. The distribution of Mn in enamel and coronal dentine showed a distinct and reproducible pattern. In enamel, the ⁵⁵Mn:⁴³Ca ratio was highest at the outer edge of enamel (range=0.57 to 4.74) for approximately 20-40 μm but was substantially lower in deeper layers (range=0.005 to 0.013). The highest levels of Mn were observed in dentine immediately adjacent the pulpal margin (⁵⁵Mn:⁴³Ca range=2.27 to 6.95). Importantly, a clearly demarcated high Mn zone was observed in dentine at the incisal end of the teeth. Using confocal laser scanning microscopy to visualize the neonatal line, this region was identified as being in the prenatally formed dentine. The high-resolution map of the spatial distribution of Mn in human primary teeth highlighted specific reproducible patterns of Mn distribution in enamel and coronal dentine.

Tooth element levels indicating exposure profiles in diabetic and hypertensive subjects from Mysore, India

Element contents of teeth elucidate exposure nature, but less is known about association of tooth element concentrations of diabetics and hypertensives with exposure profile. Present study aims to estimate copper, chromium, iron, zinc, nickel, and lead concentrations in the permanent teeth of control, diabetic, and hypertensive subjects from Mysore. The results show that lead levels of teeth (Pb-T) are higher in the hypertensives and diabetics, whereas copper levels of teeth (Cu-T) are lower in the hypertensives and users of stainless steel utensils than that of controls and users of mixed utensils. The elevated Cu-T levels found in the users of mixed utensils that being made of several metals are ascribed to leaching effect of sour and spicy food of Indian cuisine. The element levels were influenced by diet (Zn-T), place of living, sex and income (Pb-T) of the subjects, but not by age, drinking water from different sources, and certain habits viz., smoking, alcohol consumption, chewing betel, and nut. Thus, it is evident that high Pb-T and low Cu-T levels may be related with diabetes and hypertension and high Pb-T and Cu-T levels, respectively, in the urbanites, and the users of mixed utensils may show different exposure profiles from environment and utensils.

Potentiometric stripping analysis of zinc and copper in human teeth and dental materials

Potentiometric stripping analysis (PSA) with oxygen as the oxidant has been used to determine soluble zinc and copper levels in exfoliated human teeth (all of which required extraction for orthodontic reasons) and commercial dental materials. The soluble zinc and copper contents of teeth were slightly below the zinc and copper contents in whole teeth reported by other researchers, except in the case of tooth with removed amalgam filling. Soluble zinc and copper concentrations of the dental materials and metal ceramic crowns were 0.50-6.30, and of 2.00-4.30 microg/g, respectively. The results of this work suggest that PSA may be a good method for zinc and copper leaching studies during the investigation of dental prosthetic materials' biocompatibility. Corrosive action of acidic media as evidenced by SEM micrographs caused the leaching of metal ions from teeth.