The Structural Features Of Different Teeth And Their Inspiration For Mineral Synthesis

The fantastic structure-forming process in biological systems is the results of evolution of many billions of years,which efficiently and accurately fabricate biominerals under environmentally benign conditions.In contrast to our present technological world where harsh conditions are commonly prerequisites for materials fabrication.Therefore,the natural structure-forming process itself of biominerals is worth learning by scientists for developing new synthesis techniques for advanced materials,which can be refereed as“bio-process inspired synthesis”.Enamel is known as the densest material in vertebrates,its composition and structure originate from a highly complex design system.The elaborate architecture and excellent mechanical properties of enamel attracted the attention of researchers,devoting their long-term efforts to mimic their structure and performance in vitro.However,few researchers have focused on another important keypoint“growth rate”of teeth.There are significant differences among the tooth growth rate of various species.This research work for the first time compared the mineralization process of teeth with significantly different growth rates,such as human teeth,rat teeth and shark teeth.Then we revealed the crucial factors affecting the rate of growth,and explored their intrinsic mechanisms for fabricating materials with high efficient.Through studying the microstructure and composition of human teeth,rat teeth and shark teeth,we established the intrinsic relationship among microstructure,composition and growth rate,and explored the important factors affecting the rate of tooth growth.The following important results are obtained:?1?Different microstructures:There are three growth directions in shark tooth enamel and mouse tooth enamel,and two ones in human tooth enamel.While human enamel has the most accurate assembly form,shark tooth enamel is the least assembly.Meanwhile,the building blocks of teeth are also different.?2?Different inorganic composition:The main composition of human teeth and rat tooth enamel is hydroxyapatite,and shark tooth enamel is fluoroapatite;?3?Different organic composition:The content of organisms in human teeth is the largest than shark teeth and rat teeth.The organic content in rat teeth is the least.In order to demonstrate the effects of architecture and composition on tooth growth rate,we selected the fresh slices of human,rat and shark teeth as the growth substrate,and induced the growth of hydroxyapatite or fluoroapatite on the surface of teeth slices.Our result have shown that fresh slices failed to induce the synthesis of hydroxyapatite,but all can induce the formation of columnar fluoroapatite.Among them,fluoroapatite with a similar enamel-column structure was successfully obtained on the surface of shark teeth slices,organized fluoroapatite nanorods with a diameter of approximately 100-150 nm?shark enamel column diameter approximately 100 nm?.In addition,the growth rate of fluoroapatite on the surface of different teeth slices was also different,the growth rate of fluoroapatite on shark tooth enamel is fastest,human teeth is the slowest.To further demonstrate the effect of dental organic composition on the growth rate of teeth,human tooth amelogenin?recombinant Amelx-his protein?was successfully obtained using recombinant protein technology.The peristaltic pump was chosen to precisely control the ion dripping rate in the mineralization system,which solved the problem of loss of mineralization activity due to self-assembly agglomeration of amelogenin.The results showed that recombinant amelogenin?Amelx-his?did not show a significant role in the regulation of hydroxyapatite growth;but displayed the effect in the regulation of CaCO₃ morphology and stabilization of crystal form.A thermodynamically unstable vaterite mesocrystal CaCO₃ was successfully prepared.The optimal mineralization conditions:pH=9,protein concentration 4%,and stationary mineralization time 12 h.