Mechanical properties of human enamel as a function of age and location in the tooth

Aging and the related changes in mechanical behavior of hard tissues of the human body are becoming increasingly important. In this study the influence of aging on the mechanical behavior of human enamel was evaluated using 3rd molars from young (18 ≤ age ≤ 30 years) and old (55 ≤ age) patients. The hardness and elastic modulus were quantified using nanoindentation as a function of distance from the Dentin–Enamel Junction (DEJ) and within three different regions of the crown (i.e. cervical, cuspal and inter-cuspal enamel). Results of the evaluation showed that the elastic modulus and hardness increased with distance from the DEJ in all three regions examined, regardless of patient age. The largest increases with distance from the DEJ occurred within the cervical region of the old enamel. Overall, the results showed that there were no age-dependent differences in properties of enamel near the DEJ. However, near the tooth’s surface, both the hardness (p < 0.025) and elastic modulus (p < 0.0001) were significantly greater in the old enamel. At the surface of the tooth the average elastic modulus of “old” enamel was nearly 20% greater than that of enamel from the young patients.

[1]  G W Marshall,et al.  Evaluation of a new modulus mapping technique to investigate microstructural features of human teeth. , 2004, Journal of biomechanics.

[2]  L. Hsiung,et al.  Depth-dependent mechanical properties of enamel by nanoindentation. , 2007, Journal of biomedical materials research. Part A.

[3]  M F Teaford,et al.  The effect of prism orientation on the indentation testing of human molar enamel. , 2007, Archives of oral biology.

[4]  J. M. ten Cate,et al.  The Effect of Adjacent Dentine Blocks on the Demineralisation and Remineralisation of Enamel in vitro , 2005, Caries Research.

[5]  Naoki Fujisawa,et al.  Elastic modulus and stress-strain response of human enamel by nano-indentation. , 2006, Biomaterials.

[6]  M. Swain,et al.  Mechanical properties across hypomineralized/hypoplastic enamel of first permanent molar teeth. , 2004, European journal of oral sciences.

[7]  J. Kirkham,et al.  Dental enamel : formation to destruction , 1995 .

[8]  T. Cate,et al.  Oral histology: Development, structure, and function , 1980 .

[9]  R. Ritchie,et al.  A transmission electron microscopy study of mineralization in age-induced transparent dentin. , 2005, Biomaterials.

[10]  G. Willems,et al.  Hardness and Young's modulus determined by nanoindentation technique of filler particles of dental restorative materials compared with human enamel. , 1993, Journal of biomedical materials research.

[11]  A. Boyde,et al.  Relating Developing Surface To Adult Ultrastructure in Chiropteran Enamel By Sem , 1987, Advances in Dental Research.

[12]  M. Snead,et al.  Biological Organization of Hydroxyapatite Crystallites into a Fibrous Continuum Toughens and Controls Anisotropy in Human Enamel , 2001, Journal of dental research.

[13]  Mehdi Balooch,et al.  Nanoindentation and storage of teeth. , 2002, Journal of biomechanics.

[14]  D. Arola,et al.  Effects of aging on the mechanical behavior of human dentin. , 2005, Biomaterials.

[15]  J. Quinn,et al.  Indentation brittleness of ceramics: a fresh approach , 1997 .

[16]  Energy absorption characterization of human enamel using nanoindentation. , 2007, Journal of biomedical materials research. Part A.

[17]  R. F. Bunshah,et al.  Fracture Toughness of Human Enamel , 1981, Journal of dental research.

[18]  D. Arola,et al.  Age, dehydration and fatigue crack growth in dentin. , 2006, Biomaterials.

[19]  F. Cui,et al.  Property variations in the prism and the organic sheath within enamel by nanoindentation. , 2005, Biomaterials.

[20]  E. Eanes.  Enamel Apatite: Chemistry, Structure and Properties , 1979, Journal of dental research.

[21]  E Romberg,et al.  Indentation Damage and Mechanical Properties of Human Enamel and Dentin , 1998, Journal of dental research.

[22]  G. Pharr,et al.  An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments , 1992 .

[23]  C. Davidson,et al.  The double origin of enamel fluid , 2007 .

[24]  D. Weber.  Sheath configurations in human cuspal enamel , 1973, Journal of morphology.

[25]  T. P. Weihs,et al.  Nanoindentation mapping of the mechanical properties of human molar tooth enamel. , 2002, Archives of oral biology.

[26]  C. Davidson,et al.  In vivo enamel fluid movement. , 2007, European journal of oral sciences.

[27]  N Meredith,et al.  Measurement of the microhardness and Young's modulus of human enamel and dentine using an indentation technique. , 1996, Archives of oral biology.

[28]  M V Swain,et al.  Mechanical properties and microstructure of hypomineralised enamel of permanent teeth. , 2004, Biomaterials.

[29]  G W Marshall,et al.  Mechanical properties of human dental enamel on the nanometre scale. , 2001, Archives of oral biology.

[30]  R O Ritchie,et al.  Age-related transparent root dentin: mineral concentration, crystallite size, and mechanical properties. , 2005, Biomaterials.

[31]  Robert H. Anderson.  Handbook of Microscopic Anatomy: Series Editors: A. Oksche, L. Vollrath Volume 2/Part 7: Cardiac Muscle E.D. Canale, G.R. Campbell, J.J. Smolich, J.H. Campbell Springer-Verlag, Berlin/Heidelberg/New York/Tokyo, 1986; 318 pp.; DM460; ISBN 3-540-16379-4 (Berlin), 0-387-16379-4 (New York) , 1987 .

[32]  I. Mjör,et al.  Age-related changes in hardness and modulus of elasticity of dentine. , 2006, Archives of oral biology.

[33]  W. Robinson,et al.  Spherical indentation of tooth enamel , 1981 .

[34]  G. Marshall,et al.  Local mechanical and optical properties of normal and transparent root dentin , 2001, Journal of materials science. Materials in medicine.