Type of presentation: Poster

ID-13-P-3085 TEM study of the structural transformations of fluorapaite obtained from shark teeth.

Solla E. L.1, Balboa E.2, Coladas P.2, Rodríguez-Valencia C.2, López-Álvarez M.2, Serra J.2, González P.2
1Servicio de Microscopía Electrónica, CACTI, Universidade de Vigo, As Lagoas-Marcosende, 36310 Vigo, Spain. , 2New Materials Group, Applied Physics Department, School of Industrial Engineering, Institute of Biomedical Research of Vigo, University of Vigo, As Lagoas-Marcosende, 36310 Vigo, Spain.
esolla@uvigo.es

The shark teeth present a great similarity in composition to the mammalian teeth and bone tissue, which consists of a mineral phase of calcium-deficient carbonated hydroxyapatite together with fluorapatite, where hydroxil is partially replaced by fluorine [1]. Thus, this fishing by-product has a potential application in the medical field as a bone filler material in orthopedical surgery, enamel regeneration and other dental and maxillofacial treatments.

In the present work, a TEM analysis was performed to study the structural transformations during the fabrication process of these materials to obtain the final bioceramic product. Teeth from two species of shark (Isurus oxyrinchus and Prionace glauca) were boiled in water to remove organic remains from the jaw. Then, the whole natural pieces were subjected to a ball mill (Retsch MM2000) during 5 minutes and with an oscillation frequency between 3-35 Hz to obtain a powder. This powder was pyrolyzed at 950 ºC during 12 hours with a heating ramp of 2 ºC/min and an ending cooling ramp of 20 ºC/min to remove the organic matter.
In order to assess the composition of the starting material, SAED patterns were obtained from the non-pyrolized powder (Fig.1). The analysis of the electron diffraction pattern (Fig.2) allowed for the indexing of the (002), (121) and (1-12) reflections as found in the crystal structure resolved by Hughes et. al. [2], thus confirming the presence of fluorapatite on the shark teeth. However, when the same analysis was conducted on the pyrolized sample (Fig. 3), the SAED diffraction spots could no longer be attributed to fluorapatite but to the formation of whitlockite, as indicated by the indexing of the (223), (0-14) and (131) corresponding to the crystal structure described by Calvo et. al. [3]. It has already been reported that the thermal treatment of biological hydroxyapatites induces the formation of whitlockite [4], that albeit having a different crystal structure, it has also shown excellent biocompatible properties [5].

REFERENCES
[1] J. Enax, O. Prymak, D. Raabeb, M. Epple. J. Struct. Biol. 178 (2012), 290-299.
[2] J.M. Hughes, M. Cameron, K.D. Crowley, Am. Mineral. 74 (1989), 870-876.
[3] C. Calvo, C. Gopal 60 (1975). Am. Mineral. 120-133.
[4] A. Kohutová, P. Honcová, L. Svoboda, P. Bezdička, M. Maříková, J. Therm. Anal. Calorim. 108 (2012), 163–170.
[5] H.L. Jang, K. Jin, J. Lee, Y. Kim, S.H. Nahm, K.S. Hong, K.T. Nam, ACS Nano 8 (2014), 634-641.

FEDER MARMED Atlantic Area Transn. Prog., Xunta de Galicia GRC2013-008, Fundación Mutua Madrileña 2013/14. M. López-Álvarez thanks FP7/ REGPOT-2012–2013.1 n° 316265, BIOCAPS.

Fig. 1: TEM image of a particle of shark tooth powder prior to pyrolization. The circle indicates the area where the SAED aperture was placed.

Fig. 2: SAED pattern showing the reflections indexed as fluorapaite.

Fig. 3: TEM image of a particle of 1000 ºC pirolyzed shark tooth powder. The circle indicates the area where the SAED aperture was placed.

Fig. 4: SAED pattern showing the reflections corresponding to the presence of whitlockite.