Effects Of Enamel-dentinal Junction And Tooth Type On The Mechanical Properties Of Human Teeth

Teeth are the most important chewing organ in the body, teeth have a lot to do with pronunciation, breathing and facial beauty. The structure of the tooth is more complex, teeth are composed of enamel with high hardness in out layer and dentine with high toughness in the inner layer, The structure between the two part is enamel-dentinal junction. In addition, functions and stress of the same column on different types of teeth are different. At present, there are few researches about effects of enamel-dentinal junction and tooth type on the mechanical properties of human teeth. The mechanical properties of natural biological material is closely related to microscopic structure. So, it is necessary to explore effects of enamel-dentinal junction and tooth type on the mechanical properties of human teeth, the research can provide theoretical guidance for dental restorative materials bionic design.In this thesis, we compared the mechanical properties and tribological properties of human incisor and molar the in vitro experiment, using a variety of means to compare the related mechanical properties parameters of incisor and molar. In addition, this thesis also studied the dentine and enamel-dentinal junction to prevent crack extension in tooth enamel. The main research results are as follows:(1) Enamel-dentinal junction is the combination of enamel and dentine interface layer, hardness and elastic modulus from the enamel to dentin layer showed a trend of the change of gradient descent. The combination of enamel and dentine strength greater than 40 Mpa. Abaqus finite element analysis results show that the existence of the nature of tooth enamel and dentine of crack extension in the enamel of blocking effect, stress and damage of the enamel layer has the improvement and protection.(2) This thesis compared the mechanical properties of natural incisor and molar, The mechanical properties of incisor and molar does exist differences, hardness, elastic modulus, fracture toughness and impact resistance of incisor were greater than molar, The sliding wear morphology has no obvious difference, But the friction coefficient of incisor was obviously higher than that of molars, the mechanical properties of differences reveals the complexity of biological composite material structure and performance. Mechanical properties of the teeth closely related with its structure, cutting tooth enamel of calcium and phosphorus ratio and hydroxyapatite grain size were greater than molar teeth enamel, This suggests that the inorganic phase content in the cutting tooth enamel is greater than the molar teeth enamel, the microstructure differences lead to the different mechanical properties of two types of teeth.