Application of metallic profiling of teeth for
Environmental and Forensic Science
S. Hendry1, C. Morrison1, A. Hursthouse1, K. Spohr2
1 School of Science,2School of Engineering University of the West of Scotland, Paisley, UK
Email contact: [email protected]
Introduction
Male teeth
The human body can be exposed to various environments and surroundings that
promote transfer of metals to the body in the air from pollution, soil and water from
contamination and also in our diet from food sources containing metals.
Male Arthritis teeth
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Metals found in the body will have dietary and/or environmental causes while analysis
may help to indicate exposure to particular metals or geographical information
assisting in both environmental science and forensic investigations.
1
2
1000
3
4
1
ug per gram
ug per gram
10000
1000
2
3
4
100
5
100
5
10
10
1
Al
Why Teeth
Ca
Fe
K
Mg
Mn
Na
Pb
Sr
Al
B
Ba
Ca
Fe
K
Mg
Mn
Na
Pb
Sr
0.1
The healthy males teeth follows similar trends between elements however varies more
significantly between samples in the arthritic teeth, specifically between calcium, iron,
manganese and lead. This suggests that the male produce a more significant fingerprint of their
historical content.
• They are the hardest structures of the human body, relatively stable, not subject
to turnover
• Suitable for metal analysis over longer time scales and when investigating time
specific concentrations of metals
Females Arthritis teeth
Female teeth
Pre requisite to Human Teeth
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10000
1000
1000
1
ug per gram
ug per gram
• Relatively easy to collect following routine extraction or shedding.
100
4
100
5
10
1
1
Al
B
Ba
Ca
Fe
1
Tooth samples from Sprague Dawley rats were donated from another research
project within UWS in accordance with the home office regulations.
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3
10
Given the complexity of the matrix and potential problems associated with digestion
and analysis methodology, a pilot study has been initiated using non human sources
of sample to optimise the approach.
2
K
3
4
Mg
Mn
Pb
Sr
Al
Zn
5
Ba
Ca
Fe
K
Mg
Na
Pb
Sr
0.1
Preliminary conclusions
Destructive and non-destructive tests were performed on the teeth via inductively
coupled plasma atomic emission spectroscopy (ICP-AES) and scanning electron
microscopy (SEM).
Preliminary assessment suggests variability between :
• Male / Female
• Healthy / Unhealthy
• Health / Treated
• Location of tooth
SEM was used to assess the feasibility for surface analysis by defining the transition
effects between the root to the crown, gender and disease
With enough replication to be consistent however will warrant further investigation of
normalisation methods to remove natural variability
Treated rats
ICP-AES was used to infer the cumulative trace metal levels.
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ug per gram
The tooth samples were weighed out to approximately 0.02 ± 0.0035g and
transferred to a 50ml digestion vessel.
1. 5ml of concentrated Nitric acid was added to the samples and left at room
temperature overnight.
Series1
1000
Series2
Series3
100
2. Samples were then refluxed at 110°C for 15minutes and then digested at the
same temperature for 60minutes.
1
Al
B
Ba
Bi
Ca
Fe
K
Mg
Results
Teeth from 50 males and 50 females were collected (50 left and 50 right for both
genders) establishing 4 reference standards Male Left, Male Right, Female left
and Female right. The relative standard deviations of the replicates are shown in
the figure below
% Relative Standard Deviations of self certified reference
material
Figure 1: Arthritic rats right tooth and elemental distribution
100
Na
Pb
Se
Sr
Zn
Element
Weight%
Atomic%
Element
Weight%
Atomic%
OK
10.59
18.18
OK
7.00
12.26
Na K
31.02
37.07
Na K
33.87
41.26
Mg K
0.34
0.39
Mg K
0.05
0.06
Al K
0.33
0.34
Al K
0.14
0.14
Si K
0.25
0.25
PK
7.01
6.22
PK
3.49
3.16
Cl K
34.06
26.40
Cl K
47.19
37.28
Ca K
16.65
11.41
Ca K
8.01
5.60
Totals
100.00
Totals
100.00
Figure 2: Rats left tooth and elemental distribution
Element
Weight%
Atomic%
OK
3.51
6.25
Na K
38.27
47.35
0.18
PK
2.53
2.32
1.62
1.48
Cl K
49.09
39.39
Cl K
52.68
41.88
Ca K
6.61
4.69
Ca K
4.12
2.90
Totals
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Totals
100.00
Element
Weight%
Atomic%
OK
5.26
9.26
Na K
35.83
43.93
Mg K
0.32
0.37
Al K
0.17
PK
Figure 3: Arthritic rats left tooth and elemental distribution
Ongoing Work
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80
70
• Complete analysis on the (ICP-MS) for the bulk of the remaining samples, still
waiting to be analysed.
80.00
60
50
60.00
Mn
Figure 4: Rats right tooth and elemental distribution
All samples were ran alongside blank digestion standards, spiked samples both
pre and post digestion and certified reference materials. The percentage recovery
of the certified reference material is shown in the figure below.
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The ICP results can be backed up with SEM
results. SEM can offer a quick evaluation of
the variability present for the surface of the
tooth.
However the SEM is hindered by its
sensitivity resulting in the appearance of less
variability when compared to the whole tooth.
10
3. Samples were allowed to cool to room temperature and then made up to 50ml
(Rats Food) / 25ml (Rats Teeth) with UHP water. A further 1:10 dilution is carried
out for ICP-MS analysis.
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After looking at rats that have been treated
for arthritis, irrespective of gender it suggests
that the disease itself is the cause of the
elemental concentrations and as a result has
a more balanced distribution of composition.
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Methodology
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• Identify external influences such as age, gender, diet, weight, disease and
sampling
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30
20.00
20
10
0.00
Al
Ba
Ca
Co
Cr
Cu
Fe
K
Mg
Element
Limestone
Bush and Branches
Mn
Pb
Sr
Zn
0
0
Soil
5
10
Female Left
15
20
Female Right
25
Male Left
30
Male Right
Zn
Comparison between healthy female rats and arthritic teeth it can be seen that there is less
variation between samples with the arthritic teeth with regards to calcium but varies less with
lead.
The study acts as a prerequisite enabling the methodology to be validated on a
similar structure and composition matrix. In this study, we used lower left and right
mandibular incisors, which continually erupt and contain all stages of tooth
formation.
Certified reference material recovery
Zn
1
Teeth are an ideal site to study exposure to trace metals since
% Recovery
Ba
35
40
• Statistically characterise the effects of metal composition between rats teeth and
rats diet