Effect of trimming line design and edge extension of orthodontic aligners on force transmission: An in vitro study

Elshazly, Tarek M.; Keilig, Ludger; Salvatori, Damiano; Chavanne, Philippe; Aldesoki, Mostafa; Bourauel, Christoph

doi:10.1016/j.jdent.2022.104276

Cited by 22 publications

(29 citation statements)

References 35 publications

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“…From the time when the CAD/CAM process and the intraoral scanners found their way into aligner therapy, the manufacturing workflow of aligners became completely digital with less effort and time [4]. The force system of orthodontic aligners is not fully understood yet, consequently, their clinical outcomes are less predictable [5][6][7][8]. However, it is postulated that force with aligners is generated via two mechanisms acting in the same time.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Thermomechanical Aging of Orthodontic Aligners on Force and Torque Generation: An <em>in vitro</em> Study

Elshazly¹,

Nang²,

Golkhani³

et al. 2023

Preprint

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The aim of the study is to investigate the effects of artificial aging by thermocycling and mechanical loading on force/torque delivery by thermoplastic orthodontic aligners. Ten thermoformed aligners made of Zendura™ thermoplastic polyurethane sheets were aged over two weeks in deionized water by thermocycling alone (n=5) and by both thermocycling and mechanical loading (n=5). The force/torque generated on upper second premolar (Tooth 25) of a plastic model was measured before aging (as control), and after 2, 4, 6, 10, and 14 days of aging, using a biomechanical set-up. Before aging, the extrusion-intrusion forces were in the range of 2.4 to 3.0 N, the oro-vestibular forces were 1.8 to 2.0 N, and the torques on mesio-distal rotation were 13.6 to 40.0 Nmm. Pure thermocycling had no significant effect on the force decay of the aligners. However, there was a significant decrease in force/torque after 2 days of aging for both thermocycling and mechanical loading aging group, which is no longer significant over 14 days of aging. In conclusion, artificial aging of aligners in deionized water with thermocycling and mechanical loading results in a significant decrease in force/torque generation. However, the mechanical loading of aligners has a greater impact than thermocycling alone.

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Section: Introductionmentioning

confidence: 99%

“…The performance of orthodontic aligners is strongly affected by the utilized material [5,6,8,12,13]. Optimally, orthodontic materials should exert continuous light force over time, and the material should always return to its original shape after removal from the mouth [7,14].…”

Section: Introductionmentioning

confidence: 99%

Effect of Thermomechanical Aging of Orthodontic Aligners on Force and Torque Generation: An <em>in vitro</em> Study

Elshazly¹,

Nang²,

Golkhani³

et al. 2023

Preprint

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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%

“…The materials used have a strong effect on the performance of orthodontic aligners [5,6]. Ideally, the orthodontic material should deliver a continuous light force throughout the treatment period [10,11].…”

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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Are aligners capable of inducing palatal bodily translation or palatal root torque of upper central incisors? A biomechanical in vitro study

Elkholy

Weber

Repky³

et al. 2023

Clin Oral Invest

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Objectives Previous studies have shown that aligners have limited ability to control root movements. The purpose of this study was to investigate which modification geometry and foil thickness are optimal for generating the force-moment (F/M) systems required for palatal root torque of maxillary central incisors. Materials and methods Tooth 11 was separated from a maxillary acrylic model and connected to a movement unit via a 3D F/M sensor. Different modification geometries (crescent, capsular, double-spherical) with different depths were digitally implemented in the labio-cervical region of tooth 11 to induce an increased contact force. We evaluated the F/M systems exerted by aligners with thicknesses of 0.4–1.0 mm. F/M measurements were taken with tooth 11 in the neutral position and during palatal displacement of tooth 11 (simulating its initial clinical movement). Results The mechanical requirements of palatal root torque are a palatally directed force (− Fy) and a palatal root torquing moment (− Mx). These requirements were reliably achieved with modification depths > 0.5 mm. The modification depth and foil thickness had a significant influence on − Fy magnitudes (linear mixed-effect models, p < 0.01). With the 0.75-mm aligners combined with 1.5-mm deep modifications, the palatal root torque range (palTR) started after an initial palatal crown displacement of 0.09, 0.12, and 0.12 mm for the capsular, crescent, and double-spherical modification geometries, respectively. Conclusions A relatively early start of the palatal torque range (after a 0.1-mm palatal crown displacement) and appropriate − Fy magnitudes were achieved with 0.75-mm-thick aligners containing 1.5-mm deep capsular or crescent pressure regions. Subsequent clinical trials are required to confirm the clinical effects of these modifications. Clinical relevance In vitro testing indicated that modified aligners are capable of generating the F/M components required for palatal root torque of upper central incisors.

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Effect of trimming line design and edge extension of orthodontic aligners on force transmission: An in vitro study

Cited by 22 publications

References 35 publications

Effect of Thermomechanical Aging of Orthodontic Aligners on Force and Torque Generation: An <em>in vitro</em> Study

Effect of Thermomechanical Aging of Orthodontic Aligners on Force and Torque Generation: An <em>in vitro</em> Study

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

Are aligners capable of inducing palatal bodily translation or palatal root torque of upper central incisors? A biomechanical in vitro study

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