Computer-aided finite element model for biomechanical analysis of orthodontic aligners

Elshazly, Tarek M.; Bourauel, Christoph; Aldesoki, Mostafa; Ghoneima, Ahmed; Abuzayda, Moosa; Talaat, Wael; Talaat, Sameh; Keilig, Ludger

doi:10.1007/s00784-022-04692-7

Cited by 26 publications

(23 citation statements)

References 50 publications

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“…First, the 0.75 mm-thick aligner produced more significant distal tipping tendency. A previous study demonstrated that thicker aligners produced stronger orthodontic forces under the same magnitude of deformation [20]. Logically, the orthodontic force in the distal direction produced by 0.75 mm-thick aligners for incisors was more significant.…”

Section: Discussionmentioning

confidence: 84%

“…Although many studies have analyzed the biomechanics of aligner-attachments and torque control of anterior teeth, the thickness of aligner has not been investigated in full detail, even though this factor is closely associated with other important features such as the forces and moments they generate and the displacement tendency of teeth [18,19]. Elshazly and Elkholy demonstrated that orthodontic forces increased as aligner thickness increased, thus proving that there was a significant influence of the aligner thickness on their biomechanical functionality [20,21]. Relevant studies previously focused on aligner thicknesses ranging from 0.5 mm to 0.75 mm [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

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The three-dimensional displacement tendency of teeth depending on incisor torque compensation with clear aligners of different thicknesses in cases of extraction: a finite element study

et al. 2022

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Background Despite the popularity of clear aligner treatment, the effect of the thickness of these aligners has not been fully investigated. The objective of this study was to assess the effects of incisor torque compensation with different thicknesses of clear aligner on the three-dimensional displacement tendency of teeth in cases of extraction. Methods Three-dimensional finite element models of the maxillary dentition with extracted first premolars, maxilla, periodontal ligaments, attachments, and aligners were constructed and subject to Finite Element Analysis (FEA). Two groups of models were created: (1) with 0.75 mm-thick aligners and (2) with 0.5 mm-thick aligners. A loading method was developed to simulate the action of clear aligners for the en masse retraction of the incisors. Power ridges of different heights were applied to both groups to mimic torque control, and the power ridges favoring the translation of the central incisors were selected. Then, we used ANSYS software to analyze the initial displacement of teeth and the principle stress on the PDL. Results Distal tipping, lingual tipping and extrusion of the incisors, distal tipping and extrusion of the canines, and mesial tipping and intrusion of the posterior teeth were all generated by clear aligner therapy. With the 0.5 mm-thick aligner, a power ridge of 0.7 mm could cause bodily retraction of the central incisors. With the 0.75 mm-thick aligner, a power ridge of 0.25 mm could cause translation of the central incisors. Aligner torque compensation created by the power ridges generated palatal root torque and intrusion of the incisors, intrusion of the canines, mesial tipping and the intrusion of the second premolar; these effects were more significant with a 0.75 mm-thick aligner. After torque compensation, the stress placed on the periodontal ligament of the incisors was distributed more evenly with the 0.75 mm-thick aligner. Conclusions The torque compensation caused by power ridges can achieve incisor intrusion and palatal root torque. Appropriate torque compensation with thicker aligners should be designed to ensure bodily retraction of anterior teeth and minimize root resorption, although more attention should be paid to the anchorage control of posterior teeth in cases of extraction.

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Section: Discussionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

The three-dimensional displacement tendency of teeth depending on incisor torque compensation with clear aligners of different thicknesses in cases of extraction: a finite element study

et al. 2022

View full text Add to dashboard Cite

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“…Thanks to CAD/CAM and intraoral scanner technology, the workflow has become much easier and faster [4]. The mechanical performance of orthodontic aligners is still vague [5][6][7]. It is assumed that the returning forces of the aligners on the target tooth are generated by two mechanisms: initially by the local elastic deformation of the aligner body in the contact area with the misaligned target tooth and then comes the elastic deformation of the entire aligner, since the entire aligner body is lifted in the area of the misaligned target tooth while it is fixed to the other teeth by friction [8,9].…”

Section: Introductionmentioning

confidence: 99%

“…Elshazly at al. [6], based on their finite element study, postulated that the deformation of the aligner is a combination of stretching (direct proportional with deflection) and bending (direct proportional to the third power of the thickness).…”

Section: Introductionmentioning

confidence: 99%

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Effect of Aging of Orthodontic Aligners in Different Storage Media on Force and Torque Generation: An in vitro Study

Elshazly¹,

Nang²,

Golkhani³

et al. 2022

Preprint

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The aim of this study is to study the effect of aging in different media (deionized water and artificial saliva) on the force/torque generation by thermoplastic orthodontic aligners. Ten thermoformed aligners made of Essix ACE® thermoplastic sheets were aged in deionized water and in artificial saliva over two weeks at 37 C, five in each medium. The force/torque generated on upper second premolar (Tooth 25) of a resin model was measured at day 0 (before aging), 2, 4, 6, 10, and 14, using a biomechanical test set-up. The results showed that the thermocycling of aligners has no significant impact on their force/torque decay. No significant differences were also found in force/torque between the aligners stored in deionized water nor artificial saliva. The vertical extrusion-intrusion forces were measured in the range of 1.4 to 4.6 N, the horizontal oro-vestibular forces were 1.3 to 2.5 N, while the torques on mesio-distal rotation were 5.4 to 41.7 Nmm. It could be concluded that the influence of saliva on the mechanical properties can be classified as insignificant, and no significant difference between artificial aging in deionized water or artificial saliva was observed.

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Effect of material composition and thickness of orthodontic aligners on the transmission and distribution of forces: an in vitro study

Elshazly,

Bourauel,

Ismail

et al. 2024

Clin Oral Invest

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Objectives To investigate the effects of material type and thickness on force generation and distribution by aligners. Materials and methods Sixty aligners were divided into six groups (n = 10): one group with a thickness of 0.89 mm using Zendura Viva (Multi-layer), four groups with a thickness of 0.75 mm using Zendura FLX (Multi-layer), CA Pro (Multi-layer), Zendura (Single-layer), and Duran (Single-layer) sheets, and one group with a thickness of 0.50 mm using Duran sheets. Force measurements were conducted using Fuji® pressure-sensitive films. Results The lowest force values, both active and passive, were recorded for the multi-layered sheets: CA Pro (83.1 N, 50.5 N), Zendura FLX (88.9 N, 60.7 N), and Zendura Viva (92.5 N, 68.5 N). Conversely, the highest values were recorded for the single-layered sheets: Duran (131.9 N, 71.8 N) and Zendura (149.7 N, 89.8 N). The highest force was recorded at the middle third of the aligner, followed by the incisal third, and then the cervical third. The net force between the incisal and cervical thirds (FI-FC) showed insignificant difference across different materials. However, when comparing the incisal and middle thirds, the net force (FI-FM) was higher with single-layered materials. Both overall force and net force (FI-FM) were significantly higher with 0.75 mm compared to those with a thickness of 0.50 mm. Conclusions Multi-layered aligner materials exert lower forces compared to their single-layered counterparts. Additionally, increased thickness in aligners results in enhanced retention and greater force generation. For effective bodily tooth movement, thicker and single-layered rigid materials are preferred. Clinical relevance This research provides valuable insights into the biomechanics of orthodontic aligners, which could have significant clinical implications for orthodontists. Orthodontists might use this information to more effectively tailor aligner treatments, considering the specific tooth movement required for each individual patient. In light of these findings, an exchangeable protocol for aligner treatment is suggested, which however needs to be proven clinically. This protocol proposes alternating between multi-layered and single-layered materials within the same treatment phase. This strategy is suggested to optimize treatment outcomes, particularly when planning for a bodily tooth movement.

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Computer-aided finite element model for biomechanical analysis of orthodontic aligners

Cited by 26 publications

References 50 publications

The three-dimensional displacement tendency of teeth depending on incisor torque compensation with clear aligners of different thicknesses in cases of extraction: a finite element study

The three-dimensional displacement tendency of teeth depending on incisor torque compensation with clear aligners of different thicknesses in cases of extraction: a finite element study

Effect of Aging of Orthodontic Aligners in Different Storage Media on Force and Torque Generation: An in vitro Study

Effect of material composition and thickness of orthodontic aligners on the transmission and distribution of forces: an in vitro study

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