The Influence Of Carbon Films On The Friction And Wear Of Orthodontic Archwire And Bracket Under The Control Of Pretension Force

For the beauty and health of teeth,more and more people choose to wear orthodontic fixed appliances to align their teeth.Common fixed appliances consist of archwire and bracket,the generated friction force when the two are combined will affect the orthodontic effect.Therefore,reducing the friction between the archwire and bracket has become a hot topic in the field of orthodontics.Applying pretension force to the archwire is a key operation during orthodontic treatment.Pretension force has a great impact on the correction effect,but currently there are few systematic researches on pretension force,and the relationship between pretension force and friction force between the archwire and bracket is unclear.Aiming at the above problems,this article carried out the " the influence of carbon films on the friction and wear of orthodontic archwire and bracket under the control of pretension force",providing experimental basis and reference for clinical applications of pretension force and carbon film in orthodontic treatment.In order to investigate the effect of pretension force on the friction behavior of the sliding contact of archwire and bracket,commercially available archwires and brackets are employed as experimental materials,and then a custom designed reciprocating archwire-bracket friction and wear experimental equipement is applied to performed a systematic experiment in dry and artificial saliva environments with pretension force ranging from 10 N to 17 N.The experimental results showed that under the same pretension force of 10 N,the larger the wire size,the smaller the average friction coefficient,the 0.019 inch stainless steel archwire had the lowest average friction coefficients of 0.36 and 0.40 under dry and artificial saliva environments,respectively.0.017 inch stainless steel archwire had the lowest average friction coefficient of 0.35 under pretension force of 12 N;0.019 inch stainless steel archwire had the lowest average friction coefficient of 0.30 under pretension force of 14 N.For 0.017 inch stainless steel archwire,the pretension force mainly affected the contact position with the bracket;for 0.019 inch stainless steel archwire,the pretension force mainly affected the contact force between itself and the bracket.To explore the effect of pretension force on friction under different size of archwires,the static simulation of archwires was performed using ANSYS software.The results showed that the pretension force affects the force and strength of archwires with different stiffness.Specifically,under the same pretension force,the greater the stiffness of the archwire,the better the friction performance.In order to reduce the friction force between the archwire and bracket,carbon films were deposited on the surface of the stainless steel archwires by using the ECR plasma sputtering apparatus under different substrate bias voltages.The composition and structure characterization results showed that the carbon films under the +5 V and +10 V bias voltages are amorphous carbon films,whereas graphene nanocrystalline carbon films are fabricated at+20 V and +50 V.Friction performance of the carbon film was evaluated using the archwirebracket friction experimental equipment,the results showed that the carbon films prepared have excellent low friction and wear characteristics,and could significantly reduce the friction coefficient between the archwire and the bracket about 70% in the dry and artificial saliva environment,and the wear reduction was also observed.With the increase of substrate bias voltage from +5 V to +50 V,the average coefficient of friction decreased from 0.16 to 0.12,and the maximum static friction coefficient decreased from 0.27 to 0.17.To further verify the feasibility of the application of the carbon film in the actual oral environment,friction experiments were performed after the immersion of carbon films in artificial saliva solution.The experimental results showed that the carbon films have uniform corrosion on the surface after the immersion test in artificial saliva.The average friction coefficients increased from0.12 to 0.19,and the maximum static friction coefficient increased from 0.19 to 0.28.The low friction mechanism of the carbon film in the artificial saliva environment was discussed according to the experimental results.The graphene nanocrystalline carbon film could quickly form a transfer film due to the formation of graphene nanocrystallites,then the graphene nanocrystallites are compressed and sheared.The flat graphene nanocrystallite could reduce the van der Waals force between the friction pairs,so that it could quickly get into the low friction stage and maintain a stable friction coefficient with the help of the saliva adsorption film.