Biomechanical Effects of Different Auxiliary–Aligner Designs on the Rotation of an Upper Canine: A Finite Element Analysis of a Specific Patient

Abstract

Aim: The objective of this research has been to apply a specific simulation to a patient to assess the biomechanical consequences of rotating an upper canine tooth through different attachment–aligner configurations and to predict the most efficient design using a three-dimensional finite element model of a full maxillary arch of a specific patient. Materials and methods: This was obtained by combining Cone-Beam Computed Tomography (CBCT) with the aim of reconstructing tooth roots and bone tissues, and Surface Structured-Light Scanning for creating digital tooth crown models from the patient’s impressions. This model was imported into the finite element solver (Ansys® 17). Three different attachment–aligner combinations were created through the exploitation of computer-aided design (CAD) procedures, i.e., without attachments, with a couple of attachments and with an attachment and a pressure point. For each simulation, the resulting force–moment (MF) system applied by the aligner to the target tooth, as well as the tooth displacement and rotation, was computed using a workstation based on Intel Xeon CPU E3-1245 v3@3.40 GHz and 16 GB RAM. Simulations reported that by adding the pressure point and the attachment to the standard aligner the amount of Moment z (Mz) delivered to the tooth increased almost two times. Results and conclusions: The maximum tooth displacement (0.85 mm) was obtained with the attachment and pressure point aligner, while the lowest (0.058 mm) was obtained with use of a couple of attachments. Both the attachment and the pressure point have the potential to enhance the appliance’s effectiveness. Particularly, the pressure point showed a higher influence on the load absolute value. The method applied in the present study should be used to retrieve the best design configuration for each patient and specific tooth movement.

Finite element analysis of the mechanical behavior of 3D printed orthodontic attachments used in aligner treatment

“…The consistency, viscosity and other composite properties can influence the position and shape of attachments, factors that are essential for the efficacy of the attachments 5 . The 3D printable resin used to create the proposed protocol simulation models has greater mechanical proprieties than the conventional flowable composite resins used in aligner treatment.…”

“…Studies suggest that higher bonding forces lead to superior retention of the attachments 25 . The Finite Element Method numerical technique used to analyze the proposed method of 3D printed aligner attachments versus the conventional method is widely used in the orthodontic field to analyze the stress strain distribution of orthodontic appliances 5 , 26 and has long been validated as a tool that provides acceptable accuracy to predict clinical outcomes 7 . Given the small contact area analized and identical simulation environments, the present study uses simplified models in FEM simulations 27 , the aim being to reduce the number of nodes and the overall output time of the analysis.…”

“…In modern orthodontics, due to an increased demand for aesthetics and health, orthodontic clear aligner treatments have gained popularity among adult and adolescent patients 1 . This type of treatment requires digitally designed attachments, made of polymeric resins 2 – 4 , applied on the enamel surface that maximize the contacts between the trays and the teeth, providing the orthodontic force and improving the retention of the aligner 5 , 6 .…”