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

Abstract

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.)

Clear aligner orthodontic therapy of rotated mandibular round-shaped teeth: A finite element study

“…According to Gomez et al, 5 teeth, attachments, and aligners were considered as isotropic and homogeneous materials. Teeth and attachments were considered as a unique body with rigid stiffness behavior.…”

“…3,4 Forces originating from metal wire and bracket interactions are transmitted to tooth structures causing displacement; on the contrary, CAT outcomes are the result of a predetermined mismatch between tooth and aligner, which coincides with the desired position of the tooth. 3,5 The final dental position is reached by sequential aligners worn by patient 22 h/d, which progressively reposition the teeth by small amounts. 3,5,6 Additionally, several studies demonstrated that auxiliaries such as attachments and elastics are mandatory in CAT to achieve the predicted results.…”

“…3,5 The final dental position is reached by sequential aligners worn by patient 22 h/d, which progressively reposition the teeth by small amounts. 3,5,6 Additionally, several studies demonstrated that auxiliaries such as attachments and elastics are mandatory in CAT to achieve the predicted results. 3 Tooth shape could influence the efficiency of CAT 7,8 during correction of malalignment due to the geometric interaction between teeth and aligners.…”

Optimization of configuration of attachment in tooth translation with transparent tooth correction by appropriate moment-to-force ratios: Biomechanical analysis

“…The aligner, which corresponds to the new desired tooth position, is fitted on the dental arch, producing in each mismatch a force system that is directly transmitted to the tooth, generating the mechanical-biological chain of events that results in a new position of the tooth [15]. The interaction between the aligner and the tooth is complicated because of the complex and irregular shape of the aligner.…”

“…Gomez, et al [15] concluded that the plastic aligner system's biomechanical supplementary composite attachments generate the force system required to produce bodily tooth movement; the absence of biomechanical supplementary composite attachments can result in undesired inclination of the tooth during translation movements.…”