Modelling strategies for the advanced design of polymeric orthodontic aligners

In the last decade, orthodontic removable thermoplastic aligners have become a common alternative to conventional fixed brackets and wires. However, the wide spread of this typology of orthodontic treatment was not followed by an adequate scientific investigation about its biomechanical effects onto the teeth. In the present work, a patient-specific framework has been developed with the aim of simulating orthodontic tooth movements by using plastic aligners. A maxillary and a mandibular dental arch were reconstructed by combining optical and radiographic imaging methods. A Finite Element (FE) model was then created to analyze two different aligner configurations. In particular, the effect of a non-uniform aligner’s thickness and of a customized initial offset between the aligner and the patient dentition were studied. The force-moment systems delivered by the aligner to a mandibular central incisor during labiolingual tipping, and to a maxillary central incisor during rotation were analyzed and discussed.