Korean J Orthod.  2025 Jan;55(1):58-68. 10.4041/kjod24.029.

Evaluation of the effect of attachments on torque control of palatally positioned maxillary lateral teeth with clear aligners: Finite element analysis

• Karsli N
• Ocak I
• Gökcek S
• Özsoy

• KMID: 2565029
• DOI: http://doi.org/10.4041/kjod24.029

Abstract

Objective
The effect of different attachment positions on torque control during the labialization of maxillary lateral incisors with clear aligners was evaluated using finite element analysis.
Methods
Anatomical data acquired through cone-beam computed tomography, combined with the design of 0.625-mmthick aligners and horizontal attachments, were integrated into the software. Six distinct simulations were generated: (1) attachment-free, (2) labial attachment placed gingivally, (3) labial attachment placed mid-crown, (4) labial attachment placed incisally, (5) palatal attachment, and (6) attachment placed labially and palatally. The evaluation was performed using a default aligner activation of 0.25 mm.
Results
The crown of the lateral incisor demonstrated labial movement, while the root exhibited palatal movement in all models. Group 6 showed the lowest crown and root displacements on both axes, whereas the attachmentfree group exhibited the greatest crown movement. The aligner experienced maximum deformation at the incisal edge, with deformation progressively decreasing towards the gingival region. Group 6 demonstrated the least deformation of all groups. The Von Mises stresses in the periodontal ligament (PDL) were most pronounced at the gingival level, with higher values on the palatal side than on the labial side.
Conclusions
The use of attachments, particularly the combination of labial and palatal attachments, enables a more precise labialization process, helping to reduce tipping. Increasing crown movement of the lateral incisor elevates stress within the PDL, with the highest stress observed in the palatal region at the gingival level.

Keyword

Clear aligners; Lateral incisor; Torque; Finite element analysis

Figure

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  Figure 1 Mathematical model showing anatomical structures and clear aligner. A, A section of an existing model; B, Maxillary tissues created based on patient data, and clear aligner; C, Methematical model.

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  Figure 2 Models prepared for different study protocols. A, Group 1 (no attachment); B, Group 2 (gingivally positioned labial attachment); C, Group 3 (mid-crown labial attachment); D, Group 4 (incisally positioned labial attachment); E, Group 5 (palatal attachment); F, Group 6 (combined attachments).

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  Figure 3 Boundary conditions.

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  Figure 4 Displacement pattern of the lateral incisor with the activation of the 0.625 mm thick clear aligner (material). A, Group 1 (no attachment); B, Group 2 (gingivally positioned labial attachment); C, Group 3 (mid-crown labial attachment); D, Group 4 (incisally positioned labial attachment); E, Group 5 (palatal attachment); F, Group 6 (combined attachments).

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  Figure 5 Clear aligner deformation values. A, Group 1 (no attachment); B, Group 2 (gingivally positioned labial attachment); C, Group 3 (mid-crown labial attachment); D, Group 4 (incisally positioned labial attachment); E, Group 5 (palatal attachment); F, Group 6 (combined attachments).

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  Figure 6 Von Mises stress values in periodontal ligament at 0.25 mm activation of the clear aligner. A, Group 1 (no attachment); B, Group 2 (gingivally positioned labial attachment); C, Group 3 (mid-crown labial attachment); D, Group 4 (incisally positioned labial attachment); E, Group 5 (palatal attachment); F, Group 6 (combined attachments).

Reference

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