Objective: The study aimed to clarify the compositions of 14 brands of superelastic NiTi orthodontic wires. Materials and Methods: The compositions were analysed through scanning electron microscopy and energy-dispersive X-ray microanalysis. The wires were tested in differential scanning calorimetry to find the transitional temperature range. Results: The compositions were nickel (50.085%-51.605%), titanium (46.675%-48.140%), copper (0.995%-1.155%), aluminum (0.220%-1.325%), chromium (0%-0.275%) and iron (0%-0.030%). None contained cobalt. G&H, Ormco, AMDG, IMD, Smart, TruFlex, Force 1, NIC, Sentalloy, Ortho Supply and Flexwire were almost or completely austenitic in the oral environment, whereas Highland, Grikin and Unitex were a mixture of austenitic and martensitic phase. The wires showed austenitic finish temperatures ranging from 17°C to 59°C. Conclusions: The results show that NiTi orthodontic arch wires have differences in composition and phase transformation. This information is valuable to evaluate differences in NiTi orthodontic wires for clinical use.