Static and Cyclic Load-Deflection Characteristics of NiTi Orthodontic Archwires Using Modified BendingTests

Equiatomic Nickel-Titanium  (NiTi or Nitinol) have the ability to return to a former shape when subjected to an appropriate thermomechanical procedure. One of the most successful applications of Nitinol is orthodontic archwire. The best features of these wires are super-elasticity, the phenomena that causes easy engagement (loading conditions). Super-elastic nitinol wires deliver clinically desired light continuous force during deactivation (unloading conditions), enabling effective tooth movement with minimal damage for periodontal tissues. In this research a special three point bending fixture invented and designed to determine the superelastic property in clinical conditions, and the wire samples was held in the fixture similar to oral cavity. The superelastic behavior has been investigated by focusing on bending time, temperature and number of cycles which affects the energy dissipating capacity. Experimental results show that the NiTi archwires are well suited for cyclic load-unload dental applications. Results show reduction in superelastic property for used archwires after long time static bending.