The Study On The Mechnical Properties Of The Microstructure And The Micro-friction Behavior Of The Human Tooth Enamel

With the improvement of the living standards, the people's diet is more and more diversified, which bring out the problem of the tooth wear more and more prominent. Therefore, the use of the excellently matching restoration to repair the teeth with excessive wear have a strongly realistic importance. Understanding of the micro-mechanical properties of human enamel is not only to provide necessary scientific guidance for the research and development of the biomimetic dental restoration materials, but also conducive to enrich and develop the bio-tribology.In this paper, the mechanical properties of human tooth enamel rods were studied using nano-indentation technique. Then, the elastic modulus and hardness were tested to draw the map of mechanical distribution in an enamel rod. Furthermore, the microwear of the tooth enamel was studies on the nano-scratch tester. The effect of the array orientation of the enamel on the enamel microwear was also studies. Main conclusions can be summarized as follows:1. Both the hardness and elastic modulus were differed with the location in an enamel rod. The mechanical properties of the central region are obviously better than those of the edge region. In addition, the hardness and elastic modulus of the rod head area were larger than those of the enamel rod tail area, the average hardness and elastic modulus in the head are 4.17±0.29 GPa and 3.69±0.29 GPa, relatively, and those of the rod tail were 85.9±6.2 GPa and 79.7±6.7 GPa, relatively.2. The friction and wear mechanism of the enamel on the mirometre scale is similar to macrowesr. Under the variable loads from 0～50mN, enamel deformation experienced from a totally zero-wear elastic deformation to plastic flow, and ultimately lead to surface crushing brittle spalling. In the initial of the frictional contact at the low load, the rigid-flex microstructure of the enamel make the enamel represent a good deformation and coordination capacity, the main deformation of the surface is elastic; With the load increasing, Indentation depth of the tip is gradually beyond the limits of the elastic deformation of the enamel, then the plastic deformation is appeared, the enamel surface shows traces of plastic flow; As the load continues to increase, the enamel surface come into being brittle fracture. With the sliding of the tip, the surface of the enamel have some brittle delamination, the wear debris is seen, the substantial wear is occurred.3. The friction and wear in different section plane of the enamel are significant different. The friction properties on the occlusal-section are better than that on axis-section, the friction coefficient and wear are both lower than axis-section. On the occlusal-section, the enamel has better friction stability than that on the axis-section. Enamel demonstrated anisotropic tribological properties in the axial. When scratching ran perpendicular to enamel rods, both the friction curve and the morphology of scratch trace were similar to those in the occlusal section. When scratching ran parallel to enamel rods, brittle delamination occurred at lower load. Higher friction coefficient and more significant material removal were observed at same load.