Mechanical Characterization of Orthodontic Archwires in a Pseudo In-Vivo Context

Abstract

Orthodontic fixed appliances are used to correct dental malocclusions by optimizing tooth movement and associated bone remodelling. Currently, orthodontic archwires made of shape memory alloys (SMAs) are widely used to initiate these treatments. We conduct experiments on SMA wires in pseudo in-vivo conditions, complementary to ISO standards, to assess the influence of temperature and humidity and to highlight their expected mechanical behaviour for clinical use. For this, an in-house built measurement device was developed to carry out experiments at controlled temperatures (21°C and 35°C) and in dry or wet conditions (artificial saliva). The dental arch was reproduced by 3D printing. The results show that the temperature has a major influence on the delivered forces whereas wet or dry conditions seem to have less impact. Also, we emphasize that at 35°C (in mouth conditions), in wet or dry conditions, SMAs superelasticity is only effective for displacements up to about 3 mm when an entire dental arch is considered.