Torquing an upper central incisor with aligners--acting forces and biomechanical principles

Objective: To evaluate whether overloading of teeth can be avoided by utilizing aligners with reduced thicknesses of 0.4 mm or 0.3 mm. Materials and Methods: The experimental setup included an acrylic maxillary jaw model with tooth 11 separated and fixed via a 3-D force-moment transducer to a hexapod for experimental movement. Aligners tested were fabricated on duplicate stone models using commercially available polyethylene terephthalate glycol (PET-G) foils with thicknesses between 0.5 and 0.75 mm, and novel 0.4-mm-and 0.3-mm-thick foils. With the test aligner seated, 11 was bodily displaced in a labiopalatal direction in the range of 60.25 mm while all six force-and-moment components exerted on this tooth were registered. Results: With the thinnest commercially available 0.5-mm aligner, median forces of À7.89 N and 8.37 N were measured for the maximum 0.25-mm movement of 11 in a labial and palatal direction, respectively. In comparison, force values were 35% and 71% lower for the novel aligners with a thickness of 0.4 mm and 0.3 mm, respectively. Conclusions: Novel ''leveling'' aligners with reduced thickness may reduce overloading of individual teeth during aligner therapy. Due to form instability of 0.3-mm aligners, we suggest a novel sequence of 0.4-0.5-0.75 mm for aligner systems using several foil thicknesses for load graduation within single setup steps. This would combine low stiffness of the initial aligner and relatively constant load increases throughout the treatment. (Angle Orthod. 2016;86:883-890)

Section: Introductionmentioning

confidence: 99%

Forces and moments delivered by novel, thinner PET-G aligners during labiopalatal bodily movement of a maxillary central incisor: An in vitro study

Elkholy

Schmidt

Jäger

et al. 2016

“…Although aligner-based rotation 11 and torque 12,13 movement have been explored, neither the mechanics of bodily tooth movement nor the role of the biomechanically enhancing composite attachments has been considered. The goal of this study is to describe, using a FE model, the force system and displacement patterns produced by plastic aligners in mechanics intended to produce bodily tooth movement with and without composite attachments.…”

Section: Introductionmentioning

confidence: 99%

Initial force systems during bodily tooth movement with plastic aligners and composite attachments: A three-dimensional finite element analysis

Gómez

Peña

Martínez

et al. 2014

147

117

Objective: To describe, using a three-dimensional finite element (FE) model, the initial force system generated during bodily movement of upper canines with plastic aligners with and without composite attachments. Materials and Methods: A CAD model of an upper right canine, its alveolar bone and periodontal ligament, thermoformed plastic aligner, and two light-cured composite attachments were constructed. A FE model was used to analyze the effects of imposing a distal movement condition of 0.15 mm on the aligner (simulating the mechanics used to produce a distal bodily movement) with and without composite attachments. Results: In terms of tension and compression stress distribution, without composite attachments a compression area in the cervical third of the distal root surface and a tension area in the apical third of the mesial surface were observed. With composite attachments, uniform compression areas in the distal root surface and uniform tension area in the mesial root surface were observed. Compression areas in the active surfaces of the composite attachments were also observed. In terms of movement patterns, an uncontrolled distal inclination, with rotation axis between the middle and cervical root thirds, was observed without composite attachment. Distal bodily movement (translation) was observed with composite attachment. Conclusions: In a three-dimensional FE analysis of a plastic aligner system biomechanically supplementary composite attachments generate the force system required to produce bodily tooth movement; the absence of biomechanically supplementary composite attachments favors the undesired inclination of the tooth during the translation movements. (Angle Orthod. 2015;85:454-460.)

“…[1][2][3] As has been shown before, during this deformation the aligner tends to lift up from the teeth, especially near the misaligned tooth, and therefore becomes deformed in the shape of a bow. 4 This mechanism is one among others evoking the forces acting on the tooth to be moved.…”

Section: Introductionmentioning

confidence: 53%

“…The modular measuring device has been described in detail before. [1][2][3][4] After rigging the measuring device, an impression (Tetrachrom, Kanidenta, Herford, Germany) with the measuring tooth in the zero position was taken and then a plaster model (GC Fujirock EP, GC Germany GmbH, Munich, Germany) was produced with a height of 20 mm parallel to the occlusal plane. Subsequently, 20 identical plaster copies (GC Fujirock EP, GC Germany GmbH, Munich, Germany) of the model were made using Adisil blue 9:1 (SILADENT Dr. Bö hme & Schö ps GmbH, Goslar, Germany).…”

Section: Methodsmentioning

confidence: 99%

The influence of occlusal forces on force delivery properties of aligners during rotation of an upper central incisor

Hahn¹,

Engelke²,

Jung³

et al. 2011

Objective: To determine the forces and moments delivered to a maxillary central incisor during rotation with aligners when a simulated occlusal force generated during swallowing acts on the appliance. Materials and Methods: Five identical appliances were manufactured from four different starting materials (Erkodur 0.8 mm and 1.0 mm; Biolon 0.75 mm and 1.0 mm). An upper central incisor fixed in a measuring device was rotated around its central axis in 0.5-degree steps up to 610 degrees with the appliance fixed in place. An occlusal force of 30 N generated during swallowing was simulated with a weight positioned on the appliance. For statistical analysis, the moments Tz (rotation) and forces Fz (intrusion) at a deflection of 60.34 mm to the incisor edge (65 degrees rotation) were tested. Means and standard deviations for Tz and median and 25% and 75% quartiles for Fz were calculated. An analysis of variance was performed.