Experiment Study On The Anterior Segment Force Attenuation Of The Archwire With Tip-back

Objective:The study was to research the mechanical properties of four different stainless steel wires with three different tip-back bend angles, and the variousness with relation to the period of loading under artificial saliva environment, and to provide reference for clinical practice when using tip-back bend validly.Materials and Methods:Four types of stainless steel round wire of 0.016 inches being used popularly in orthodontics were selected. All groups were all prepared with tip-back bends of angles 20°,30°,40°.To simulate maximum intrusive force with the different tip-back bends of archwires when using in anterior teeth, a comparative study was about intrusive force of each experimental sample. All datas were measured by The Instron Universal Testing Machine.A Stress/strain curve was prepared; in addition, these samples were observed which were maintained in artificial saliva environment of 37℃under constant loading force. The forces at six different moments in 8 weeks were recorded respectively.(at 24-hour point,48-hour point,1-week point,2-week point,4-week point,8-week point). Then the percentage of residual force was calculated, and the results analysed.Results:1.All the samples indicated different intrusive forces. In all types of wires, the intrusive force of wire with the tip-back angle of 40°was the largest, the mean force was between 95.7g-100.0g, the intrusive force of wire with the tip-back angle of 30°in the middle, the mean force between 74.3g-79g, and the intrusive force of wire with the tip-back angle of 20°the weakest, the mean force between 47.0g-49.5g.The intrusive forces of the Ordinary stainless wires were the largest with the same angle, the mean force of the wire with angle 40°were 100.0g,the mean force of the wire with angle 30°79.0g,and the mean force of the wire with angle 20°49.6g.2.It is found that the intrusive forces of the archwires with the same tip-back bend angle were different,almost all the datas showed the force of Australian wire were weaker than that of Ordinary stainless steel wire.3.When given the same tip-back bend angle,with the same type wire, the intrusive force of the anterior teeth attenuated as the time went on.the initial 4 weeks is more than the later 4 weeks in simulated clinical usage in artificial saliva environment of 37℃.4.The influence of types and angles on force attenuatation of the wires was statistically significant. Different types' wires had different force attenuatation and the same is true of the tip-back bend angles, the larger the tip-back angle was,the more quickly the force attenuated.Conclusions:1.Intrusive forces had relation to the tip-back bend angles and the types of arch wires.2.The intrusive force attenuated as the loading time went on,the attenuatation showed downtrend.3.The intrusive force attenuatation was related with the types and tip-back bend angles of the wires.