Force-Deflection behavior of NiTi archwire towards frictions’ effect in orthodontic levelling treatment

• Main Authors: Ahmad, M. N., Mahmud, A. S., Razali, M. F., Ng, C. W., Razak, T. A. A.
• Format: Conference Proceeding
• Language: English
• Subjects: Archwires; Bend tests; Brackets; Configurations; Deactivation; Deflection; Intermetallic compounds; Leveling; Martensitic transformations; Nickel base alloys; Nickel titanides; Orthodontics; Polytetrafluoroethylene; Room temperature; Shape memory alloys; Sliding friction; Stainless steels; Wire
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/5.0178565

This work aims to evaluate the force-deflection behavior of NiTi shape memory alloy archwire towards the effect of friction in orthodontic leveling. A universal bending jig setup was developed to perform three-point bending, two-bracket bending, and three-bracket bending tests at room temperature (27°C). The three-point bending setup follows the ISO 15841 standard and is then modified to compensate for the setup of bracket bending tests. Two different wire sizes were used; 0.014-in and 0.016-in NiTi round archwire, and 0.016-in × 0.022-in and 0.018-in × 0.025-in NiTi rectangular archwire, coupled with 0.022-in stainless steel brackets. The polytetrafluoroethylene (PTFE) bracket is resembling a frictionless bracket used as a control experiment. The force-deflection behavior of the NiTi archwire mounted on the PTFE bracket/support showed a flat plateau of force at stress-induced martensitic phase transformation (SIMT) at activation and deactivation stages, in all bending configurations. However, the use of the stainless-steel bracket/support causes a positive and negative gradient in the activation and deactivation of the force. The force gradient is, even more, steeper in the three-bracket configuration compared to the two-bracket configuration. On the other hand, the sliding friction is determined at the bending point while the binding friction is determined at the bending point. The frictions that have occurred vary depending on the size and shape of the wire. The presence of friction increased the force required to deflect the orthodontic wire to the prescribed deflection distance. The negative gradient of the force plateau during wire deactivation may prevent the deflected wire from being fully recovered.