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FEM Simulation and Investigation of Thickness Change Effect on Direct 3D Printed Clear Aligner Behaviour

Beizaei, Mahdi | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 57630 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Movahhedi, Mohammad Reza
  7. Abstract:
  8. Orthodontics, a dental specialty focused on tooth alignment, has been practiced for centuries for both therapeutic and aesthetic reasons. Traditional orthodontic treatment involves the use of brackets and wires, a method that has been widely adopted since the 1970s. However, since the early 21st century, the use of clear, polymer-based orthodontic aligners has emerged as an alternative approach for tooth straightening. Clear aligners are typically fabricated using a thermoforming process, where a sheet of polymer is heated and vacuum-formed over a 3D-printed model of the patient's teeth. A more recent approach involves the direct 3D printing of aligners based on digital scans of the teeth, eliminating the need for physical models and allowing for variable thickness. With the help of finite element analysis, this study looked into what happens when the thickness of an aligner changes in different places and how that affects the movement of orthodontic teeth. A 3D model (STP) of a mandibular dental arch was created and imported into the SolidWorks software. Periodontal ligaments were modeled, and aligners with varying localized thicknesses were designed using a generative approach. Fifteen aligner designs were simulated in Abaqus software, each with three different overall thicknesses (0.5, 0.75, and 1 mm) and four localized thickness variation protocols. The resulting initial tooth movement and stress in the periodontal ligaments were analyzed. Furthermore, the effects of aligner thickness on bone remodeling over time were simulated. The results showed that increasing the thickness of the aligner around the lateral incisors and second premolars, which are the teeth that are subjected to the most force in this treatment plan, caused up to 95% more initial tooth movement. Consequently, aligners with lower overall thicknesses but localized thicker regions can be more effective. Also, the extra stress and strain on the periodontal ligaments caused by thicker aligners sped up bone remodeling, which made teeth move faster and more evenly over time
  9. Keywords:
  10. Finite Element Method ; Remodeling ; Periodontal Ligament ; Bone Remodeling ; Variable Thickness ; Orthodontics ; Clear Aligner ; Additive Manufacturing

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