Study On The Role Of Amorphous Zirconia Treatment In Enhancing The Tribological Properties Of Human Dentin

Consisting of enamel,dentin and pulp from the outer layer to the core,human teeth are subjected to frictional loading every day and have excellent wear resistance.The dentin is inferior to the enamel in mechanical properties and wear resistance,and it is extremely sensitive to oral stimuli.Thus,the exposure of dentin to occlusal surface causes oral diseases.Hence,a timely intervention of dentin exposure is really necessary in clinic,however,nowadays,relevant treatments have some limitations,such as unsatisfactory therapeutic effect,high recurrence rate and trauma to dental tissues.It is urgent to develop efficient,convenient,and low-invasive treatments.In this thesis,the role of amorphous zirconia treatment in enhancing the tribological properties of human dentin was investigated using nano-indentation/scratch techniques,reciprocating sliding friction and wear tests,and many microscopic examinations.The findings from this study will provide valuable insights into the clinical treatments of dentin exposure.Main results and conclusions were as follows:(1)The amorphous zirconia treatment led to a deposition layer of amorphous zirconia on the surface of dentin,which had strong bonding with the dentin and effectively filled in dentin tubules.The treated dentin surface exhibited increased hardness and elastic modulus,anti-scratch performance,and then wear resistance,as compared to the original surface.Also,the amorphous zirconia treatment significantly improved the resistances of dentin surface against acid erosion and Streptococcus mutans adhesion and aggregation.It should be noted that the occlusion effect of dentin surface by amorphous zirconia treatment needs to be further improved,especially in areas of high porosity.(2)CPP-ACP treatment induced the formation of a mineralized HAP layer well-bonded to the dentin surface.As a result,dentin tubules were completely filled in and the mechanical properties of the dentine surface were increased.However,the HAP mineralized layer was vulnerable to acid erosion and not suitable to repair the exposure of dentin.(3)The combined treatment of CPP-ACP and amorphous zirconia effectively solved the problems of the unsatisfied occlusion effect of amorphous zirconia treatment and the poor erosion resistance of HAP mineralized layer.The deposition layer on dentin surface obtained from the combined treatment had excellent anti-wear and erosion performance;thus,the mechanical properties and wear resistance of the dentin surface were significantly improved.