Bond Strength of Thermoformed and 3D-Printed Aligners With Universal Primer Versus One-Step Aligner Adhesive With and Without Sandblasting: An In Vitro Study

This study evaluated the bond strength and failure modes of orthodontic auxiliaries bonded directly to different aligner materials using two adhesive strategies, with and without sandblasting treatment. Six aligner materials, including thermoplastic polymers and 3D-printed resins, were tested after thermocycling. The results showed that bond strength was significantly influenced by the aligner material and sandblasting treatment, with substrate-specific differences observed among bonding protocols. Sandblasting generally improved bond strength, although some exceptions occurred. Failure modes also varied depending on the material and were not always directly related to bond strength values. The findings highlight the importance of material-specific bonding protocols for modern thermoformed and 3D-printed orthodontic aligners.