Effects of varying attachment positions on palatal displacement of maxillary incisors with clear aligner therapy : Athree-dimensional finite element analysis.

Abstract

Clear aligner therapy (CAT) has evolved as an esthetic alternative to fixed appliance therapy. However, studies on the effects of attachments on CAT are scarce. This research was done to evaluate the effect of labial and/or palatal attachments on maxillary incisor displacement in CAT through finite element analysis (FEA). Finite element modeling was used to create four models with aligners. The following combinations were created: (1)without attachments (WO), (2)with labial attachments (WLA), (3)with palatal attachments (WPA), (4)with labial and palatal attachments (WLPA). Maximum displacement, directional displacement and stresses induced following apalatal displacement of 0.25 mm was evaluated for each of the four models. Models without attachments and those with palatal attachments showed agreater tooth movement at the incisal part of the crown (0.22 mm and 0.24 mm, respectively) than the models with labial and labiopalatal attachments (0.21 mm and 0.19 mm, respectively). The von Mises stresses were concentrated at the middle third of the roots in the model with the labial attachments (30.257 MPa), while in the other three models, stresses were concentrated at the cervical third of the roots. Maximum displacement was seen at the incisal third of the maxillary incisors in the model with palatal attachments. The model without attachment generated the highest stresses. However, labial attachments as compared to other models appear to offer some biomechanical advantage by reducing uncontrolled tipping.