13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- 5. Conclusions In this work, an energetic methodology, adapted to depth sensing indentation, has been developed to determine the enamel fracture toughness. The method is based on the contact stiffness variation due to the cracking process. The values obtained using this methodology, were compared with those provided by traditional equations based on a particular crack pattern. The results obtained were in agreement with those reported by other authors that use traditional tests to evaluate the fracture toughness of the enamel. References [1] Von Koenigswald, W., Sander, P.M., 1997. Tooth Enamel Microstructure. Von Koenigswald, W., Sander, P.M., editors. Taylor & Francis publisher. 37-41 Mortimer Street, London, W1T 3JH. [2] Eisenmann, D.R., 1998. Enamel structure. In: Oral Histology. Development, Structure and Function. AR Ten Cate editor. St. Louis, pp. 218-235. [3] Lawn, B.R., Evans, A.G., Marshall, D.B., 1980. Elastic/plastic indentation damage in ceramics: The median/radial crack system. J. Am. Ceram. Soc. 63, 574–581. [4] Anstis, G.R., Chantikul, P., Lawn, B.R., Marshall, D.B., 1981. A Critical Evaluation of Indentation Techniques for measuring Fracture Toughness: I, Direct Crack Measurements. J. Am. Ceram. Soc. 64, 533-538. [5] Niihara, K., Morena, R., Hasselmann, D.P.H., 1983. A fracture mechanics analysis of indentation-induced Palmqvist crack in ceramics. J. Mater. Sci. Lett. 2, 221-223. [6] Laugier, M.T., 1987. New formula for indentation toughness in ceramics. J. Mater. Sci. Lett. 6, 355–356. [7] Mullins, L.P., Bruzzi, M.S., McHugh, P.E., 2007. Measurement of the microstructural fracture toughness of cortical bone using indentation fracture. J. Biomech. 40, 3285–3288. [8] Ouchterlony, F., 1976. Stress intensity factors for the expansion loaded star crack. Eng. Fract. Mech. 8, 447-448. [9] Li, X., Diao, D., Bhushan, B., 1997. Fracture mechanisms of thin amorphous carbon films in nanoindentation. Acta Mater. 45, 4453-4461. [10] Oliver, W.C., Pharr, G.M., 1992. An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments. J. Mater. Res. 7, 1564-1583. [11] Garrido, M.A., Giráldez, I., Ceballos, L., Gómez del Río, M.T., Rodríguez, J., 2011. Nanotribological behaviour of tooth enamel rod affected by bleaching treatment. Wear. 271, 2334– 2339. [12] Xu, H.H.K., Smith, D.T., Jahanmir, S., Romberg, E., Kelly, J.R., Thompson, V.P., Rekow, E.D., 1998. Indentation damage and mechanical properties of human enamel and dentin. J.
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