Nano-scale mechanical and tribological properties of mineralized tissues
Research output: Thesis › Doctoral Thesis
Nanoindentation studies: * Influences of storage conditions on the elastic modulus and hardness of intertubular dentine. Results: Hanks balanced salt solution (HBSS) is a suitable fluid for storing teeth, even after two years of storage. The mechanical properties of dehydrated dentine differ considerably from immersed in HBSS condition, although the trends are preserved. The temperature of storage is likely to be an important factor for storing teeth in HBSS. * Elastic mechanical response dependence of enamel on the indenter tip angle under wet and dry conditions. The study was complemented with AFM and SEM imaging. Results: as the indenter angle increases the discrepancy wet vs. dry of the elastic modulus decreases. * Influence of viscoelastic effects in wet and dry conditions on the elastic properties of compact bone. The anisotropic behaviour in two different directions was also measured together with the influence of storage temperature on the elastic modulus. Results: the discrepancy between wet and dry results was attributed to the non mineralized phase contribution and rationalized by a simple mechanical model. Anisotropy effects could be explained in terms of deformation mechanisms inherent to the particular fibre like arrangement of lamellar bone. The effect of sub-zero storage temperatures could be clarified by the helicoidal arrangement of lamellar bone. Wear studies: * Description and evaluation of the tribological response of enamel under dry conditions with two different indenter tips. Results: two different wear mechanisms were proposed depending on the indenter tip geometry. The investigation was complemented with TEM, SEM, AFM and single scratch measurements. * Comparison of the wear response of enamel under wet and dry conditions (rounded indenter). Results: the wear mechanism for both conditions was identical. Single scratches were more sensitive to microstructural anisotropic arrangement than abrasion tests. Recovery effects were also present during sliding deformation in enamel for both wet and dry conditions, although wet (HBSS) favours this behaviour. SEM and AFM observations also indicate a better abrasion resistance for the wet than for the dry condition. * Comparison between the wear behaviors of enamel and three materials (glass and copper and silver mono-crystals). Results: enamel behaves in a brittle manner (glass like) at low loads and ductile (copper and silver like) at higher loads. SEM and AFM provided the basis to critically access the deformation behaviors.