Mechanical Properties of Thermoplastic Materials for Clear Orthodontic Aligners: A New Three‐Dimensional Experimental Setting

Introduction The mechanical properties of polyethylene terephthalate glycol modified (PETG) and thermoplastic polyurethane (TPU), commonly used in clear orthodontic aligners, significantly influence their clinical performances. Materials and Methods The present investigation involved the use of a universal testing machine equipped with specialised software to examine the mechanical behaviour of PETG and TPU aligners. The 2 materials with 2 thicknesses (0.6, 0.9 mm) were subjected to tensile tests under simulated intraoral conditions, and the responses of the materials to the varying displacements, were analysed to investigate their respective behaviours under different loading conditions. The Mann–Whitney U test was employed to assess differences between the groups. Results For 0.9 mm thickness, the stiffness between the two materials was not significantly different, except for the canine region, where TPU was significantly stiffer. Aligners fabricated in PETG with greater thickness consistently showed higher stiffness compared to thinner PETG, indicating that material behaviour varies with thickness, except for the canine region. Conclusions The mechanical behaviour of thermoplastic materials for clear aligners is influenced by material type, thickness and tooth location.