On The Relationship Between Tooth Structures/Properties And Diets Of Mammals

Mammalian teeth have an ability to adapt the new environment in evolution. Their exquisite structure and some amazing functions have been paid attention to by numerous of engineering structure designers and material researchers. Both the species and diets of mammals are various, and thus their teeth have multifarious shapes, sizes and structures. Mammals can be divided into carnivores, herbivores and omnivorous according to their diets. The various diets lead to different biting modes. And the direction of application of occlusal force is associated with biting mode. Study of the microstructure of different mammalian teeth is meaningful and helpful to biotribology research. Meanwhile, it can provide an important theoretical basis for biological bionics.In this thesis, the microstructure of several mammalian teeth was studied by means of various microsaopic examinations. Bamboo rat incisors were chosen as research samples to, study the effect of mechanical biting action on tooth enamel microstructure during its growth process. The effect of water content on the surface properties of swine tooth enamel was also been explored by in vitro testing. In addation, the relationship of tooth microwear feature with biting mode and physical properties of foods was investigated in vitro.The third chapter, the microstructure of several mammalian teeth was examined using SEM. Results indicated that the microstructure of mammalian tooth enamel was closely associated with their diets. The mechanical properties of enamel strongly depended on its microstructure.The fourth chapter investigated the effect of mechanical biting action on the microstructure of rodent tooth enamel by controlling the diets of bamboo rat. The results indicated that the enamel of the bamboo rat with bamboo diets has a more ordered microstructure than that of the bamboo rat with potato diets. Both the blood and mineral density testing results showed that nutrition almost had no influence on the microstructure of enamel. Obviously, strong mechanical biting action could promote the growth of dental tissue.The fifth chapter explored the effect of water content on enamel surface. The results indicated that the water content within the surface layer of enamel could influence the hardness and friction coefficient of enamel surface. The hardness was increased but the friction coefficient was decreased with the reduction of water content. Both the hardness and friction coefficient were restored significantlyafter the enamel was immersed in water. Further microscopic examinations by means of AFM, SXRD and GID showed that the water content could influence the bonding between the HAP particles without a denaturation of HAP on enamel surface. The bonding strength between the HAP particles was assocated with the wear resistance of enamel.The sixth chapter studied the relationship between tooth microwear feature and diets in vitro. Results indicated that tooth microwear feature was closely associated with the angle of masticatory force, not the physical properties of foods. A masticatory force perpendicular to occlusal plane (crushing) generally resulted in pits appearing on tooth surface; while a masticatory force parallel to occlusal plane (shearing) led to striations in the direction of movement. A masticatory force oblique to occlusal plane (45°) resulted in both striations and pits.