Abstract
Aim To evaluate the biomechanical effects of four different auxiliary-aligner combinations for the extrusion of a maxillary central incisor and to define the most effective design through finite element analysis (FEA). Materials and Methods A full maxillary arch (14 teeth) was modelled by combining two different imaging techniques: cone beam computed tomography and surface-structured light scan. The appliance and auxiliary element geometries were created by exploiting computer-aided design (CAD) procedures. The reconstructed digital models were imported within the finite element solver (Ansys® 17). For the extrusion movement, the authors compared the aligner without an attachment with three auxiliary-aligner designs: a rectangular palatal attachment, a rectangular buccal attachment, and an ellipsoid buccal attachment. The resulting force-moment (MF) system delivered by the aligner to the target tooth and the tooth displacement were calculated for each scenario. Results The maximum tooth displacement along the z-axis (0.07 mm) was obtained with the rectangular palatal attachment, while the minimum (0.02 mm) was obtained without any attachments. With the ellipsoid attachment, the highest undesired moments Mx and My were found. The rectangular palatal attachment showed the highest Fz (2.0 N) with the lowest undesired forces (Fx = 0.4 N; Fy = −0.2 N). Conclusions FEA demonstrated that the rectangular palatal attachment can improve the effectiveness of the appliance for the extrusion of an upper central incisor.
Highlights
Results and Discussion e finite element analysis (FEA) results were analysed for each configuration by comparing forces and moments delivered to the tooth and measured at its center of resistance (CRES) (Table 2) and the amount and direction of orthodontic movement (Table 3)
Considering the results obtained through the FEA, we can conclude the following: (i) e extrusion of an upper central incisor cannot be achieved without any attachment
(iv) e analysis of the force system delivered by the aligner to the tooth should focus on the desired loads and the effect of undesired loads should be properly taken into account, as it is a determinant when selecting the proper appliance configuration
Summary
E size of the elements has been chosen in accordance with previous studies [14, 15, 19], considering that the main purpose of this work is to compare effects of different auxiliaries on tooth movement
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