Effect of Different Anchorage Reinforcement Methods on Long-Term Maxillary Whole Arch Distalization with Clear Aligner: A 4D Finite Element Study with Staging Simulation

Abstract

The objective of this study was to examine how various anchorage methods impact long-term maxillary whole arch distalization using clear aligners (CAs) through an automated staging simulation. Three different anchorage reinforcement methods, namely, Class II elastics, buccal temporary anchorage device (TAD), and palatal TAD, were designed. Orthodontic tooth movement induced by orthodontic forces was simulated using an iterative computation method. Additionally, the automatic adjustment of the CA was simulated through the application of the thermal expansion method. The results indicated that the palatal TAD group had the largest retraction of incisors, followed by the buccal TAD group and the Class II elastic group, while the least was in the control group. The largest distal displacements and efficiency of molar distalization for the first and the second molars were noticed in the palatal TAD group. Arch width increased at the molar and premolar levels in all groups. The FEM results suggested palatal TAD had the best performance considering anterior teeth anchorage maintenance, both sagittally and vertically. However, attention should be paid to the possible increasement of arch width.

Keywords: clear aligner; finite element method; long-term simulation; molar distalization; orthodontics; tooth movement.

Figure 1

Components of the model (a) and the different anchorage design groups (b).

Figure 2

The bone remodeling simulation method, highlighting the deformation of the periodontal ligament, indicated within the blue circles. PDL, periodontal ligament.

Figure 3

(a) The establishment of the coordinate system; (b) The determination of the center point of each dental crown (yellow dots); (c) Curve fitting with a fourth-order polynomial function. The tooth numbering system adheres to the FDI tooth numbering system.

Figure 4

The ‘V pattern’ staging strategy was designed in this study: during the total 70 steps, the cells referred to designed movement were set green and the corresponding teeth were marked in blue. The tooth numbering system adheres to the FDI tooth numbering system.

Figure 5

The automated clear aligner adjustment method relies on a temperature changing method. C_i–C_j, the central point of dental crowns; P_i–P_j, the boundary points of dental crowns situated along the C_i–C_j line; Pc, the center point of P_i–P_j. L_i, the line of C_i to C_j.

Figure 6

Teeth displacement at different treatment staging steps of the four groups. Each illustration presents the comparation of the nth steps (yellow) and the (n − 10)th steps (orange) of the four groups (n = 10, 20, 30, 40, 50, 60, 70). TAD, temporary anchorage device.

Figure 7

Three-dimensional displacement of the crown points of each tooth during the 70 steps. The tooth numbering system adheres to the FDI tooth numbering system. C–C, crown point of control group; B–C, crown point of buccal temporary anchorage device (TAD) group; P–C, crown point of palatal TAD group; E–C, crown point of Class II elastic group.

Figure 8

Three-dimensional rotation of the long axis of each tooth during the 70 steps. The positive axis was established following the right-hand rule. C, control group; B, buccal temporary anchorage device (TAD) group; P, palatal TAD group; E, Class II elastic group. The tooth numbering system adheres to the FDI tooth numbering system.

Figure 9

Teeth displacement tendencies (blue arrows) at different treatment staging steps of the four groups. TAD, temporary anchorage device.

Figure 10

(a) Comparation of the initial dentition (green) and the dentition at the 70th step (yellow) of the four groups. (b) The final dentition at the 70th step of the control group (blue), buccal TAD group (red), palatal TAD group (orange), and Class II elastic group (purple). TAD, temporary anchorage device.