Electron microscopic observation of the surface of orthodontic arches reveals observable differences between new and used arches after four weeks in the mouth. This qualitative observation led us to consider their study by stimulated infrared thermography. These dental arches consist of a nickel-titanium (NiTi) shape memory alloy and are highly stressed during the stay in the mouth. Over the months, there will be evolution of their mechanical properties with multifactorial causes. In this study, we will demonstrate that it is possible to differentiate between the used arcs from the new arcs by observing their thermal response during a controlled heating.