Elemental analysis by EDX
EDX can determine the elements present, but not the bonding conditions.
We detected Ca, Cl, Cu, Fe, K, Mg, P+Pt, S, Si and Zn in the teeth (see
Figure 5). The content of each individual element, except Fe, showed
highly significant differences between the inner structure and the
surface (results from Wilcoxon-test: p<.0001*, for p-values
see Supplementary Table 1).
In the inner tooth structure, the following proportions were found
(sorted from high to low mean content): P+Pt (mean ± standard deviation:
0.56 ± 0.26 atomic %), Fe (0.53 ± 0.35), Ca (0.47 ± 0.23), S (0.34 ±
0.12), Mg (0.26 ± 0.09), Zn (0.06 ± 0.03), Cu (0.05 ± 0.04), Si (0.04 ±
0.13), Cl (0.03 ± 0.03) and K (0.03 ± 0.02). All lateral teeth showed a
rather small proportion of these elements in the inner tooth structure,
compared to the surface (see below) (see Supplementary Table 2 for
elemental content in the inner structure of the different teeth).
Between the tooth types, we could not detect significant differences by
pairwise comparison for the individual elemental content (see
Supplementary Table 3 for p-values).
In the surface layer, the following proportions were detected (sorted
from high to low mean content): Si (mean ± standard deviation: 5.79 ±
6.40 atomic %), Ca (2.28 ± 2.28), P+Pt (0.85 ± 0.60), S (0.67 ± 0.30),
Fe (0.60 ± 0.72), Mg (0.34 ± 0.20), Cu (0.14 ± 0.11), Zn (0.12 ± 0.08),
Cl (0.08 ± 0.08) and K (0.05 ± 0.03). In each tooth, especially Si and
Ca were present in larger proportions in comparison to the other
elements (see Supplementary Table 2 for elemental content of the
surfaces).
When the results from the outer tooth surface were sorted according to
the tooth region (see Figure 2 for nomenclature and 6 for results), we
found that the cusps contained highest content of all elements (Ae),
followed by the styli (terminal), the styli (bases), the sides, the
bases, and finally the bulges with the lowest content of Ae (see
Supplementary Table 4). This gradient in Ae is primarily due to the
content and distribution of Si (at cusps, mean ± standard deviation:
16.24 ± 2.76 atomic %; at bulges: 0.27 ± 0.14) and Ca (at cusps: 5.56 ±
2.01; at bulges: 0.05 ± 0.05). But the Fe content, which was present in
lower proportions, probably also contributes to the gradient, (at cusps:
1.26 ± 0.75; at bulges: 0.09 ± 0.07) (see Supplementary Table 4 for
elemental content). The decrease of Si, Ca and Fe from tip to base of
the teeth were found in each tooth type (see Supplementary Table 5 for
elemental content of the different teeth and their regions) and
differences when comparing the various regions of each tooth were highly
significant (see Supplementary Table 6 for p-values). For the
distribution of Cl, Cu, K, Mg, P+Pt, S and Zn no clear gradient could be
detected, even though most regions differed highly significantly as
determined by pairwise comparison (see Supplementary Table 6 for
p-values). These elements were present in rather small proportions in
each tooth (mean is <1 atomic %; see Supplementary Tables 2
and 4). When comparing the different teeth, we could not determine clear
differences between them (see Supplementary Figure 2). In most cases we
detected highly significant differences between the individual regions
of the surface when comparing the different teeth by pairwise comparison
for Si, Ca and Fe (see Supplementary Tables 3 for p-values).