Effectiveness of the attachment position in molar intrusion with clear aligners: a finite element study

Abstract

Objective To evaluate the biomechanical effects of different attachments’ position for maxillary molar intrusion with clear aligner treatment by finite element analysis. Methods Cone-beam computed tomography images of a patient with supra-eruption of the maxillary second molars were selected to construct three-dimensional models of the maxilla, periodontal ligaments, dentition, and clear aligner. The models were divided into four groups depending on the attachment location on the first molar: (1) no attachment (NA), (2) buccal attachment (BA), (3) palatal attachment (PA), and (4) bucco-palatal attachment (BPA). After applying an intrusion of 0.2 mm on the second molar, displacements and stress distributions of the teeth, aligner, and periodontal ligament were analyzed with the finite element software. Results All groups displayed equivalent movement patterns of aligners. The NA and BA groups showed buccal tipping of the second molar, while the PA group showed palatal tipping. The BPA group had the highest intruding value and the lowest buccal/palatal tipping value. All groups showed mesial tipping of the second molar. Stress distribution in the periodontal ligament strongly correlated with the attachment position. The BPA group showed the best stress distribution. Conclusion Combined BA and PA could effectively prevent buccal and palatal tipping and showed the best efficiency in intruding the second molar. The second molar showed an unavoidable tendency to tip mesially, regardless of the attachment position.

The predictability of arch expansion with the Invisalign First system in children with mixed dentition: a retrospective study

“…Several studies have highlighted the importance of attachment in enhancing tooth movement [25,27]. The attachments of both the buccal and palatal surfaces of the maxillary posterior teeth can increase the retention of the aligner and help move the teeth more accurately in the horizontal direction [30]. The significant effect of the number of attachments in the maxillary teeth may be due to the disadvantage of retention according to the positional characteristics of the aligners in the maxilla.…”

An in vivo evaluation of clear aligners for optimal orthodontic force and movement to determine high-efficacy and periodontal-friendly aligner staging

“…It has been reported that 70–80% of patients may require additional aligners to improve efficiency [ 27 ]. The type and position of attachments are also essential for intrusion achievement [ 28 ], but mesial and distal movement, as one of major tooth movements in alignment, was ignored. Distalization with aligners can be achieved with the sequential movement of the posterior teeth, which means the main movement occurs on the specific tooth in every alignment stage [ 10 ].…”

Effect of clear aligner type on maxillary full-arch intrusion: 3D analysis using finite element method

“…Four commercially available clear aligners with different material properties include Leon (St. Louis Park, MN, USA), Duran (Scheu-Dental, GmbH, Iserlohn, Germany), Duran Plus (Scheu Dental GmbH, Iserlohn, Germany), and Essix Plus (Dentsply Sirona Deutschland, GmbH, Bensheim, Germany) were designed with thicknesses of 0.8 mm, 1 mm, 0.75 mm, and 0.9 mm, respectively, according to their mechanical characteristics (Table 2 ), [ 27 , 28 ]. A Poisson’s ratio of 0.36 was established for the aligners based on previous studies [ 29 , 30 ]. They were considered isotropic and homogeneous materials [ 26 ].…”