Study On The Demineralization And Remineralization Behaviors Of Three Mammalian Tooth Enamel

After long terms of evolution,animal teeth possess various unique geometry shapes and microstructure and then perform their chewing functions under different oral environments.Obviously,animal teeth have excellent tribological properties,however,little is known about their tribological running mechanisms.The tribological properties of the teeth are closely associated with their acid erosion and remineralization.Thus,it is very necessary to study the erosion and remineralization behavior of mammalian teeth,which would help to fully reveal dental structure-property relationship,enrich and develop biotribology,and provide a theoretical and technical support for the bionic design of dental materials and engineering anti-wear components.In this thesis,the erosion and remineralization behaviors of bovine,porcine and canine tooth enamel were studied in vitro.Citric acid solution and artificial saliva were used as acidic media and mineralizing agent,respectively.The morphology and chemical composition of enamel surfaces were characterized by means of scanning electron microscopy and energy dispersive X-ray analysis.The nanomechanical properties and microtribological behaviors of eroded and remineralized enamel surfaces were examined using nano-indentation/scratch technique.The main conclusions are drawn as follows:(1)There were obvious differences in the erosion behaviors of three mammalian tooth enamels.Under same erosion conditions,the effect of erosion on the mechanical properties and tribological behavior were less significant for bovine tooth enamel than for either canine tooth enamel or porcine tooth enamel.The erosion damage of porcine tooth enamel was slightly severer than that of canine enamel.This should own to the microstructure difference of the three tooth enamel.Both porcine and canine tooth enamel consists of keyhole-like enamel rods and inter-rod enamel,while bovine enamel contains a plate-like microstructure.The gap between the rods and inter-rod enamel might be helpful to the permeation of acidic medium.The gaps per unit area on the three enamel surfaces were different as bovine<canine<porcine,and thus the resistance against acid-erosion of the three enamel surfaces followed the sequence as bovine>canine>porcine.(2)After 24 h remineralization in artificial saliva,a layer of mineral deposits appeared on the surfaces of the eroded bovine and porcine tooth enamel,causing their nanomechanical and microtribological properties to be remarkably improved.The deposit had similar chemical composition to the inorganic matters in the original enamel.Compared with bovine tooth enamel,the remineralization restoration of eroded porcine tooth enamel surface was more significant.The keyhole-like micro structure of porcine tooth enamel might contribute to its better remineralization ability because its more gaps between rods and inter-inter-rod enamel could promote the infiltration and deposition of mineralizer.