Affiliations: [a] CEGELY, UMR 5005, Ecole Centrale de Lyon, 69134
Ecully, France | [b] LTDS, UMR 5513, Ecole Centrale de Lyon, 69134 Ecully,
France | [c] LEIBO, EA 637, UFR Odontologie, 69 008 Lyon,
France
Abstract: Nickel-Titanium (NiTi) alloys exhibit special mechanical properties
known as shape memory effect and superelasticity. The first effect relates to
the fact that after deformation at low temperature, the material regains its
original shape after heating. The second effect denotes an unusual flexibility
of the material that is far greater than the flexibility of common metallic
materials. These properties can be put to excellent use in various biomedical
applications, such as orthodontic wires, orthopaedic implants for
osteosynthesis, stents for various applications, bone substitution materials
and experimental systems for scoliosis correction. The purpose of the present
review is to analyze in vitro NiTi biocompatibility compared to other titanium
alloys. The problem of Ni's possible toxicity is discussed. Corrosion
properties in an oral environment are investigated. The effect of surface
chemical composition and surface roughness on cell adhesion, morphology and
proliferation is shown as an example. Sterilization is taken into account and
its influence on roughness and mechanical properties, chemical composition,
wettability and bacterial adhesion inhibition is evaluated. The conclusion is
that NiTi is at least as biocompatible as conventional titanium due to the
TiO_{2} oxide layer, and that only in special chemical
conditions can Ni diffuse out of the NiTi material.
