A metallurgical characterization of ten endodontic Ni-Ti instruments: assessing the clinical relevance of shape memory and superelastic properties of Ni-Ti endodontic instruments. 

By Zinelis S, Eliades T, Eliades G. 

Date: 01/2010
Journal: JOE

Summary: 

Purpose: To evaluate the elemental composition, micro-structure and hardness of Ni-Ti endodontic instruments and to assess the relevance of shape memory and superelastic properties.

N= 5 instruments per brand (Table 1).

•After embedding the Ni-Ti instrument along their longitudinal axis in resin and metallographic preparation the elemental composition, structure and hardness were evaluated.

•SEM/energy-dispersive X-ray spectrometer (EDX), X-ray diffraction (XRD) and microhardness measurements were used to test the above parameters.

Most highlighted Results: 

  • The instruments comprised of Ni (52.1– 56.2%wt) and Ti (43.8 to 47.9%wt) .
  • XRD analysis revealed the presence of the austenitic structure in all instruments.
  • Vickers hardness values ranged from 312 (K3) to 376 VHN (Endosequence). – K3 -> Lowest microhardness  – Profile -> Intermediate microhardness – Protaper -> High microhardness.
  • No correlation was found between Ni content and hardness among the instruments tested.
  • Microstructural and hardness data confirm that the Ni-Ti instruments were manufactured by cold worked Ni-Ti and do not posses shape memory or superelastic properties.

Clinical significance:

The endodontic instruments tested were manufactured from cold worked Ni-Ti wires and thus have neither shape memory nor superelastic properties.