# Soldering and welding is not possible in:

 # Soldering and welding is not possible in:

Stainless steel wire

Elgiloy

Nitinol

TMA

The correct answer is C. Nitinol.

Limitations of NiTi wires

NiTi wires have very low formability in the clinical setting. These wires cannot be welded or soldered due to the passivating nature of titanium dioxide which is strongly adhered to the metal surface. The frictional forces in the nitinol wire are very high due to high Ti content, and therefore these wires are unsuitable for sliding tooth movements such as retraction on the wire.

NiTi wires have highest nickel content among the appliances used in orthodontics which is 55%. Although they are greatly biocompatible, however, high nickel content could be disadvantageous by causing hypersensitive reactions.

Reference: Orthodontics: Diagnosis and management of malocclusion and dentofacial deformities, OP Kharbanda, 2020