Study On The Effcts Of Oral Environment Factors On The Adsorption And Lubrication Behavior Of Salivary Proteins On Tooth Surface

As the most important component of oral chemical environment,saliva is a complex exocrine fluid secreted by three major salivary glands(parotid gland,submandibular gland,sublingual gland)and many small parotid glands.It’s widely accepted that salivary protein can selectively adsorb on enamel surface to form a nanometer-scale salivary pellicle with a multilayer structure.This film can provide effective boundary lubrication for oral cavity,being important for our daily chewing,pronunciation and swallowing.Therefore,A comprehensive understanding of the adsorption and lubrication behavior of salivary proteins not only has important theoretical value for exploring the mysteries of nature and enriching the theoretical system of bio-tribology,but also provides theoretical guidance for the development of new high-performance artificial saliva and dental materials.This will help improve the quality of life of people and has significant social and application value..The thesis mainly studies the effects of oral environment factors on the adsorption and lubrication behavior of salivary proteins on tooth surface.To do this,the adsorption and filmforming performance of salivary proteins were investigated by the dissipative quartz crystal microbalance(QCM-D),the electrophoresis,the laser particle size analyzer,the scanning probe microscopy(SPM)and so on.The mechanical and lubrication performance of salivary pellicle were explored by the nanomechanical systems and the atomic force microscopy(AFM).The main conclusions are summarized below.(1)The alcohol stimulation has a significant effect on the adsorption and lubrication behavior of salivary proteins on the tooth surface.Firstly,the introduced alcohol accelerates the saliva secretion,in which the salivary protein type is unchanged and the protein concentration is slightly increased.Secondly,the denatured protein aggregations induced by alcohol have an increased electrostatic interaction with enamel surface,and form the nonuniform salivary pellicle with decreased lubrication properties.The greater the alcohol concentration in the stimulation solution is,the more significant the above phenomenons are.The lubrication of salivary pellicle is strongly dependent on its orderly multi-layer structure.(2)The adsorption of the proteins from saliva onto enamel surface experiences two phases,saturated adsorption and oversaturated adsorption.The saturated adsorption can quickly form the stable multi-layer structure of salivary pellicle with excellent lubrication properties on the tooth surface.The supersaturated adsorbed salivary proteins have weak bonding with the sublayer and can be easily romoved,which contribute little to the lubrication of salivary pellicle.With the flow rate increasing,the saturated adsorption process is expedited,while the oversaturated adsorption is decelerated.(3)The addition of calcium ions in saliva can increase the lubricion properties of salivary proteins.Although calcium ions occupy the chelation sites on salivary proteins to weaken the electrostatic binding between the salivary proteins and the tooth surface,they can act as ligands to connect salivary proteins and promote protein aggregation,enhancing the thickness,viscoelasticity and load bearing capacity of salivary pellicle on tooth surface,and finally improving the lubrication of the salivary pellicle.(4)The lubrication of the salivary pellicle is attributed to the orderly self-assembly of salivary proteins on the tooth surface.The low-molecular-weight salivary proteins can tightly adsorb to the tooth surface by electrostatic interaction and then form a uniform density inner layer,which is likely to be a monolayer,with high bonding strength.In addition,the inner layer also serves as a decorated layer to connect the high-molecular-weight salivary proteins so as to form an outer layer,which has excellent load bearing capacity and can effectively reduce tooth wear.