CHARACTERIZATION OF THE EVOLUTIONARY ASPECTS OF GREAT WHITE SHARK TEETH BY X-RAY DIFFRACTION METHODS AND OTHER SUPPORTING TECHNIQUES
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Copyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 327
CHARACTERIZATION OF THE EVOLUTIONARY ASPECTS OF
GREAT WHITE SHARK TEETH BY X-RAY DIFFRACTION METHODS
AND OTHER SUPPORTING TECHNIQUES
Mehmet Kesmez, Jessica Lyon, David L. Cockeχ
Gill Chair of Chemistry and Chemical Engineering, Lamar University, P.O. Box 10022,
Beaumont, TX 77710, USA
James Westgate∗, Hylton McWhinney# and Tony L. Grady#
ABSTRACT
In a research program to explore evolutionary aspects of structural changes in elasmobranch
teeth, a natural composite material, dentine and enamel sections of fossilized Great White shark
teeth (ranging in age from 4, 12 and 40 million years old) have been examined by X-ray
Diffraction Methods (XRD), X-ray Photoelectron Spectroscopy (XPS), Fourier Transform
Infrared (FT-IR) Spectroscopy, and Differential Scanning Calorimetry (DSC). XRD data and
Rietveld refinement showed that Great White shark teeth have not experienced any measurable
evolutionary structural changes over millions of years. The dentine and enamel sections of the
teeth mainly consist of Fluorapatite by 1-3.7 % fluoride from elemental analysis from XPS
analysis. Also presence of Fe and Mn transition metals has been detected in some of the
specimens by XPS. FTIR results demonstrated carbonate substitution for A and B sites in some
of the specimens’ enamel and dentine sections. In addition, a medium strong band evidenced
presence of water and hydroxide overlap. Thermal analysis by DSC may conclude that Great
White shark teeth did not experience any sort of extreme thermal exposure during the
preservation time.
INTRODUCTION
Shark teeth possess a very complex hierarchical structure and their mineralogical stability is
evidenced through geologic time due to relatively preserved marine sediment conditions [1].
There are numerous persuasive reasons to examine fossil shark teeth specimens such as
biomimetics for biomaterial synthesis and composites design [2], natural history, histological,
biochemical, biological evolution and long time induced structural and chemical change in
naturally grown composite structures. In Earth Science, apatites, the major inorganic composite
constituent of shark teeth, have been used as a sensitive detector for magma derivation and
evolution [3-5]. Biogenic phosphates and carbonates present in fossil biogenic substances such
as shark teeth, fossilized bones and human dentals can be used to reconstruct paleoenvironmetal
conditions via chemical and isotopic analyses of C and O isotopes [6].
χ
Correspondent author
∗
Department of Geology, Lamar University, Beaumont, TX 77710, USA.
#
Department of Chemistry, Prairie View A&M University, Prairie View, TX 77446, USA.
This document was presented at the Denver X-ray Conference (DXC) on Applications of X-ray Analysis. Sponsored by the International Centre for Diffraction Data (ICDD). This document is provided by ICDD in cooperation with the authors and presenters of the DXC for the express purpose of educating the scientific community. All copyrights for the document are retained by ICDD. Usage is restricted for the purposes of education and scientific research. DXC Website ICDD Website – www.dxcicdd.com - www.icdd.com
Copyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 328
The structure of an elasmobranch tooth is composed of enamel, dentine, and basal plate. The
orientation of apatite crystals in enamel section will differ between species with respect to the
functionality of teeth, i.e. grinding, cutting, crushing, etc. The structure of apatite in shark teeth
most closely approximates to fluorapatite (FAp) with some hydroxide ions hydrogen bonded to
neighboring fluoride ions in a linear chain fashion along the c-axis [7-15]. Furthermore,
carbonate ions substitution for hydroxide, phosphate ions may also occur [16]. FAp,
Ca10(PO4)6F2, is the most stable apatite among hydroxylapatite, oxyapatite, carbonated apatite
[17]. FAp is hexagonal with space group P63/m and lattice parameters, a = b= 9.36 Å, c= 6.88 Å
[18]. The fluoride ions occupy the center of calcium (II) triangles found at z= ¼ and z= ¾. The
hydroxyl ions (1.40 Å) is larger with respect to fluoride ions (1.36 Å) to fit into this triangular
space, as a result the substitution of F- for OH- brings about a reduction in the volume unit cell,
the lattice becomes more dense, and its chemical stability is enhanced by virtue of electrostatic
bond formed between fluoride and adjacent ions [19].
Pliocene (4 million years old) Great White shark tooth specimen belongs to Yorktown Formation
was collected from Lee Creek Phosphate mine, Aurora, North Carolina. Miocene (12 million
years old) specimen belongs to Chesapeake Group, was collected from Stratford Cliffs,
Westmoreland Co., Virginia. Eocene (40 million years old) tooth was collected from Hardie
kaolin mine, Wilkinson Co., Georgia, and belongs to Clinchfield Formation.
A limited amount of understanding is available on the fluoridation patterns of dentine and
enamel of the elasmobranch and the effects of geologic time because of the complicated
substitution/insertion mechanisms and the scarcity of research. In this work, characterization of
elasmobranch teeth by XRD and various supporting techniques such as XPS, FT-IR and DSC
has been done to gain evidence on the evolution dependent fluoridation and its effects on the
structure of these hierarchal composite specimens. The structural and chemical effects of
fluoridation and fossilization will be discussed in context of the multi-technique characterization
data that includes the influence of iron and carbonate substitution. Authors of this study believe
that characterization of Great White shark teeth is extremely essential to have enough tools for
the investigation of complicated substitution/insertion mechanisms. Also, this paper proposes the
characterization of the teeth as the first step of the exploration of the reaction mechanism.
Further investigation will be carried to come up with reasonable explanations for the details of
the fluoridation patterns of dentine and enamel of the elasmobranch.
EXPERIMENTAL
X-ray Powder Diffraction
X-ray powder diffraction of enamel and dentine sections of the specimens was carried out with
D8 Discover with GADDS having Bragg-Brentano geometry (General Area Detector Diffraction
Systems from Bruker-AXS, Inc.). A 2000 W sealed tube with a Cu target (40 kV and 30 mA)
was used with a Ge 111 monochromator to give CuKα1 radiation (λ=1.5406Å). Data were
collected for 22Copyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 329
The sample holder was rotated about the axis defined by the planar surface of the sample to
increase the number of crystallites in differing orientations contributing to the powder pattern,
thus obtaining a better powder average. Data were collected from enamel and dentine sections of
specimens before and after thermal treatment. Powder specimens were ground in a mortar and
pestle by wet-grinding method (HPLC grade isopropyl alcohol (from Sigma-Aldrich) is used as
solvent) for 45 minutes and passed through a 400-mesh sieve to obtain homogeneous crystallite
size.
XPS Data Collection
Powder samples were collected using a Perkin Elmer PHI 5600ci X-Ray Photoelectron
Spectrometer. System background pressure was approximately in the 10-9 mbar range. Mg Kα
(1253.6 eV) radiation generated a power of 300 W using a standard dual anode source operating
at 15 kV and 20 mA. The signal from adventitious carbon (284.6 e V) was used to calibrate the
XPS data.
FT-IR Data Collection
FT-IR analysis were carried out by ATI Mattson Genesis Series using potassium bromide pellets
(sample:KBr = 1:50). The spectra were usually recorded in the range of 4000-400 cm-1 with 2
cm-1 resolution. Usually 32 scans were collected both for background and sample. Data were
collected before and after thermal treatment of specimens. Thermal treatment of samples was
done at 120 °C for 1hr and 5 hrs. The main purpose of thermal treatment was to remove
chemisorbed water and moisture from specimens.
DSC Data Collection
Powder specimens were run by STA 449C (from NETZSCH) under Helium atmosphere both as
protective and purge gases at 75 Nml/min. The heating rate was 20 °C degree/min. Specimens
were heated from room temperature to 550 °C.
RESULTS AND DISCUSSION
XRD and Rietveld Analysis
The programs GSAS [20] and TOPAS v2.1 (from Bruker-AXS, Inc.) are used for partial
Rietveld refinement with #5 background function with 6 coefficients and Chebychev background
function with 4 coefficients, respectively. The best peak shape is found to be a Lorentzian with
slight asymmetry after comparing the Rwp, Rexp, and GOF (Goodness of Fit) values for different
peak profile shapes. Rwp, Rexp values are found to be in the range of 3 to 6 and GOF ratios are
found to be around 1.05 to 1.2 for all specimens (details are not shown). In addition to
comparison of residual values obtained from both TOPAS and GSAS softwares, a visual
inspection of the fit of the observed and calculated plots established that Lorentzian with slight
asymmetry shape profile gives the best fit. Starting atomic parameters for all refinements came
from the refinement performed with by Mackie, Young [18]. The 2Θ range for partial RietveldCopyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 330
refinement was 22Copyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 331
XPS
Figures 2a-2e show XPS results.
Figure 2a) XPS spectrum for 4 million years old dentine: Ca 2 p3-Ca 2p1-Ca 2p around 345-350 eV, Fe LMM at
551, P 2s around 190 eV, P 2p around 130 eV, F 1s at 685 eV, F 2s at 30 eV.
Figure 2b) XPS spectrum for 4 million years old enamel: Ca 2 p3-Ca 2p1-Ca 2p around 345-350 eV, Fe LMM at
551, P 2s around 190 eV, P 2p around 130 eV, F 1s at 685 eV, F 2s at 30 eV.Copyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 332
Figure 2c) XPS spectrum for 12 million years old dentine: Ca 2 p3-Ca 2p1-Ca 2p around 345-350 eV, Fe 3p at 53
eV, Fe 2 p3 at 707 eV, P 2s around 190 eV, P 2p around 130 eV, F 1s at 685 eV, F 2s at 30 eV.
Figure 2d) XPS spectrum for 12 million years old enamel: Ca 2 p3-Ca 2p1-Ca 2p around 345-350 eV, Fe 3p at 53
eV, Fe 2 p3 at 707 eV, P 2s around 190 eV, P 2p around 130 eV, F1s at 685 eV, F 2s at 30 eV, Na 1s 1072 eV, Na
KLL 260 and 299 eV, Mn 2 p3 639 eV.Copyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 333
Figure 2e) XPS spectrum for 40 million years old enamel: Ca 2p3-Ca 2p1-Ca 2p around 345-350 eV, Fe 3p at 53
eV, Fe 2p3 at 707 eV, P 2s around 190 eV, P 2p around 130 eV, F 1s at 685 eV, F 2s at 30 eV.
Within the limitations of the instrument, all of the specimens were found to contain trace
amounts of Fe (III). Only both dentine and enamel sections of 12 million years old specimen
were found to contain trace amount of Mn (II). Also, only 12 million years old enamel section
was found to have trace amount of Na. Presence of carbonate in all specimens were evidenced as
a weak shoulder on the high-energy side of C 1s signal, higher oxidation states for C. Presence of
Na may indicate non-like ion substitution of Ca in the crystal structure.
From the physicochemical standpoint, incorporation of fluoride into the crystalline apatitic tooth
mineral brings about greater stability. It has been found there may be a mutual relationship
between crystallinity, physicochemical strength, and crystal strength. In general, crystallinity
reflects the physicochemical nature of the crystals, and therefore, increasing fluoride content may
increase crystallinity, i.e, crystal strength [19, 33].
Okazaki [34] suggested that Fe (II) ions would be taken by apatite crystals directly, which results
in contraction of a- and c-axis dimensions to a negligible extent. Furthermore, Okazaki also
found that crystallinity of Fe-doped apatite decreased drastically with a decrease in the Ca-
content. The presence of Fe (II) decreased solubility of apatite crystals. It may be concluded that
an increase in Fe content will affect the crystal strength due to change in physicochemical
properties of apatite crystals. The potential of trace amount of Fe and Mn present in specimens
seems it is still a mystery.Copyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 334
FT-IR
Figures 3a-3o show FT-IR spectra of all specimens before and after thermal treatment.
3a 3d
3b 3e
3c 3f
3j
3g
3h
3k
3i
3l
3m
3n
3o
Figure 3a) 4 million years old dentine after thermal treatment (heated at 120 °C for 5hr), 3b) 4 million years old
dentine after thermal treatment (heated at 120 °C for 1hr), 3c) 4 million years old dentine before thermal treatment,
3d) 4 million years old enamel after thermal treatment (heated at 120 °C for 5hr), 3e) 4 million years old enamel
after thermal treatment (heated at 120 °C for 1hr), 3f) 4 million years old enamel before thermal treatment, 3g) 12
million years old dentine after thermal treatment (heated at 120 °C for 5hr), 3h) 12 million years old dentine after
thermal treatment (heated at 120 °C for 1hr), 3i) 12 million years old dentine before thermal treatment, 3j) 12
million years old enamel after thermal treatment (heated at 120 °C for 5hr), 3k) 12 million years old enamel afterCopyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 335
thermal treatment (heated at 120 °C for 1hr), 3l) 12 million years old enamel before thermal treatment, 3m) 43
million years old enamel after thermal treatment (heated at 120 °C for 5hr), 3n) 43 million years old enamel after
thermal treatment (heated at 120 °C for 1hr), 3o) 43 million years old enamel before thermal treatment.
Phosphate absorption bands observed at 470-471, 565, 576-577, 604, 963-964, 1036-1039, 1092-
1096 cm-1. Phosphate overtones are observed between 2113-1962 cm-1.
Carbonate absorption bands found at 866, 1426-1428, 1457-1460, 1480 (weak shoulder) cm-1.
Carbonate ions may substitute at three different sites in the apatite crystal lattice: for hydroxide
(A sites), for phosphate (B sites), and for fluoride present between calcium triangles. The
carbonate absorption bands at 866 and 1457-1460 can be assigned to carbonate ions substitution
for phosphate ions in the crystal structure, this substitution is also known as B type [15, 16, 22,
23, 24, 25-32]. Carbonate absorption bands between 1472-1450 cm-1 are assigned to A type
substitution [16].
Organic absorption bands are observed between a broad range between 2986-2835 and 1727-
1570 and a medium strong band for water/hydroxide absorption between 3300-3550 cm-1 [16].
The relative intensity of water/hydroxide region did not demonstrate a significant change, it may
be concluded that both water and hydroxide are present in the specimens and are incorporated
into the structure.
Thermal Analysis
Figure 4 shows DSC data for specimens. DSC data from room temperature to 100 showed
evaporation of water from the specimens but nothing else. This may led to the conclusion that
specimens might have not experienced any extreme thermal exposure from the surrounding
environment.Copyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 336
3b
3a
Figure 3a) DSC curves for 4 and 12 million years old specimens, 3b) DSC curves for 4, 12, 43 million years old
enamel specimens.
CONCLUSION
Results obtained from XRD and various supporting techniques evidenced that Great White Shark
teeth have not experienced any measurable evolutionary structural changes in the crystal lattice
over millions of years. XRD analysis demonstrated that all specimens are composed of
Fluorapatite with some defects in the crystal structure. XPS and FT-IR analysis confirmed that
carbonate is present in the lattice and carbonate has substituted for hydroxide and phosphate.
Also FT-IR evidenced that both water and hydroxide are present in FAp crystals. DSC analysis
demonstrated that Great White Shark teeth might have not experienced any extreme thermal
exposure from external environment.
XRD combined with XPS, FT-IR and DSC gives a good research suite for teeth, a naturally
grown composite material, characterization. Further investigation of potential of Transition
Metals and reaction mechanism for fluoridation insertion/substitution reaction are needed due to
complex nature of inorganic and organic and inorganic/organic interfaces present in the tooth
structure.
ACKNOWLEDGEMENTS
The authors thank The Welch Foundation for partial support of this work under grant V-1103.
The XRD Equipment support came from the National Science Foundation under grant #
0116153.
REFERENCES
[1] M. Goto, Tsurumi U. Dent. J., 4 (1978) 85-104
[2] R. Fábián, I. Kotsis, P. Zimány and P. Halmos, Talanta, 46 (1198) 1273-1277
[3] F. Stoppa and Y. Liu, Eur. J. Mineral, 7 (1995) 391-402
[4] G. Peng, J. F. Luhr, J.J. McGee, Am. Mineral, 82 (1997) 1210-1224Copyright ©JCPDS - International Centre for Diffraction Data 2004, Advances in X-ray Analysis, Volume 47. 337
[5] S. Warner, R. F. Martin, A. F. Abdel-Rahman and R. Doig, Ontorio. Can. Mineral, 36
(1998) 981-999
[6] T. W. Venneman, E. Hegner, G. Cliff and G. W. Benz, GeoChim. Cosmochim. Acta, 65 (10)
(2001) 1583-1599
[7] R. A. Young, W. van der Lught, J. C. Elliott, Nature, 223 (1969) 729-730
[8] E. Dykes and J. C. Elliot, Calcif. Tissue Res., 7 (1971) 241-248
[9] G. Engel and W. E. Klee, J. Solid State Chem., 5 (1972) 28-34
[10] C. H. Amberg, H. C. Luk and K. P. Wagstaff, Can. J. Chem., 52 (1974) 4001-4006
[11] B. O. Fowler, Inorg. Chem., 13 (1974) 194-207
[12] F. Freund and R. M. Knobel, J. Chem. Soc. Dalton Trans., (1977) 1136-1140
[13] A. Baumer, M. Ganteaume and W. E. Klee, Bull. Minér., 108 (1985) 145-152
[14] A. Bigi, A. Foresti, A. Ripamonti and N. Roveri, J. Inorg. Biochem., 27 (1986) 31-39
[15] S. Shimoda, T. Aoba, E. C. Moreno and Y. Miake, J. Dent. Res., 69 (1990) 1731-1740
[16] S. Dahm and S. Risnes, Calcif. Tissue Int., 65 (1999) 459-465
[17] M. Mathew and S. Takagi, J. Res. Natl. Inst. Stand. Technol., 106 (2001) 1035-1044
[18] K. Sudarsanan, P. E. Mackie and R. A. Young, Mat. Res. Bull., 7 (1972) 1331-1338
[19] M. I. Kay, G. R. A. Young and A. S. Posner, Nature, 204 (1964) 1050-1052
[20] A.C. Larson and R. B. Von Dreele, “GSAS, general structure analysis system”Los Alamos
National Laboratory Report, LAUR 86-748 (1986)
[21] P.E. Mackie, R.A. Young, J. Appl. Crystallogr., 6 (1973) 26-31.
[22] G. Bonel, Ann. Chim., 7 (1972) 127-144
[23] M. Santos, P. F. González-Díaz, Inorg. Chem., 16 (1977) 2133-2134
[24] J. C. Elliott, “The interpretation of the infra-red absorption spectra of some carbonate-
containing apatites”. In: M. V. Stack and R. W. Fearnhead (eds.) Tooth enamel, John Wright:
Bristol (1965)
[25] J. C. Trombe, G. Bonel and G. Montel, Bull. Soc. Chim. France Numéro Spécial, (1968)
1708-1712
[26] D. W. Holcomb and R. A. Young, Calcif. Tissue Int., 31 (1980) 189-201
[27] R. A. Young, M. L. Bartlett, S. Spooner, P. E. Mackie, J. Biol. Phys., 9 (1981) 1-26
[28] F. C. M. Driessens, R. H. M. Verbeeck and H. J. M. Heijligers, Inorg. Chim. Acta, 80
(1983) 19-23
[29] M. Vignoles, G. Bonel, D. W. Holcomb and R. A. Young, Calcif. Tissue Int., 43 (1988) 33-
40
[30] C. Rey, B. Collins, T. Goehl, I. R. Dickson and M. J. Glimcher, Calcif. Tissue Int., 45
(1989) 157-164
[31] T. Aoba and E. C. Moreno, Calcif. Tissue Int., 47 (1990) 356-364
[32] I. Mayer, S. Schneider, M. Sydney-Zax and D. Deutsch, Calcif. Tissue Int., 46 (1990) 254-
257
[33] E. C. Moreno, M. Kresak and R. T. Zahradnik, Caries. Res., 11 (1977) 142-171
[34] M. Okazaki, “Specific physicochemical properties of fluoridated hydroxyapatites with
incorporated trace elements”. In: S. Suga and N. Watabe (eds.) “Hard tissue mineralization and
demineralization”, Springer-Verlag:Tokyo (1992)You can also read
