Abstract
Reducing the friction force between the commercial archwire and bracket during the orthodontic treatment in general dental practice has attracted worldwide interest. An investigation on the friction and wear behaviors of the uncoated and carbon film coated stainless steel archwires running against stainless steel brackets was systematically conducted. The carbon films were prepared at substrate bias voltages from +5 to +50 V using an electron cyclotron resonance plasma sputtering system. With increasing substrate bias voltage, local microstructures of the carbon films evolved from amorphous carbon to graphene nanocrystallites. Both static and stable friction coefficients of the archwire-bracket contacts sliding in dry and wet (artificial saliva) conditions decreased with the deposition of carbon films on the archwires. Low friction coefficient of 0.12 was achieved in artificial saliva environment for the graphene sheets embedded carbon (GSEC) film coated archwire. Deterioration of the friction behavior of the GSEC film coated archwire occurred after immersion of the archwire in artificial saliva solution for different periods before friction test. However, moderate friction coefficient of less than 0.30 sustained after 30 days immersion periods. The low friction mechanism is clarified to be the formation of salivary adsorbed layer and graphene sheets containing tribofilm on the contact interfaces. The robust low friction and low wear performances of the GSEC film coated archwires make them good candidates for clinical orthodontic treatment applications.
Highlights
Orthodontic treatment is the restoration of the abnormally positioned teeth for human beings, especially for children and teenagers with dramatically increasing oral health and beauty requirements in recent years [1−5]
Carbon films were fabricated on the surfaces of stainless steel archwires by using an mirror confinement electron cyclotron resonance (MCECR) plasma sputtering system
The local microstructures of the carbon films prepared by using the customized MCECR plasma sputtering system evolve from amorphous carbon to graphene nanocrystallites with the increase of the substrate bias voltage from +5 to +50 V
Summary
Orthodontic treatment is the restoration of the abnormally positioned teeth for human beings, especially for children and teenagers with dramatically increasing oral health and beauty requirements in recent years [1−5]. The fixed orthodontic appliance consisting of archwire and bracket has been extensively applied for dental clinical applications. The relative sliding of the archwire to bracket produces first static and kinetic friction forces, which greatly affects the tooth movement efficiency [6−9]. The achievement of low friction forces could strongly reduce the risk of root resorption and patient pain, shorten the treatment time, and improve both anchorage control and direction of tooth movement. Reducing the friction force (no matter static or kinetic) between the orthodontic archwire and bracket has drawn worldwide interest from clinicians in clinical stomatology fields and scientists in surface engineering fields [10−12]. Surface coating technique is clarified as one of the most effective strategies for tailoring the friction and wear behaviors of the archwire-bracket contact systems
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