Resistência mecânica de materiais plásticos para alinhadores ortodônticos: estudo laboratorial

Abstract

Aesthetic aligners were introduced in orthodontics as an innovative alternative to fixed appliances. Different thermoplastic materials can be used in their manufacture, and their biomechanical characteristics can be influenced by their properties. Furthermore this study aimed to identify factors that influence the physical properties of commercially available thermoplastic materials commonly used by orthodontists.Methods: Four different plastics used for the production of aesthetic orthodontic aligners were selected: ACE 035 Essix, C+ Essix, Crystal 0.75, Crystal 1.0. All materials were analyzed before and after thermoplasticization. The materials were divided into 8 groups with 20 specimens each. A traction test was performed, and the following variables were analyzed: elastic deformation, Young modulus, and fracture behavior.Results: The greatest elastic deformation was found in the groups with 100% PETG in the composition, opposing the groups that have polypropylene in the composition, with the lowest stretch tension. Young's modulus for groups without PETG in the composition had lower values. On the other hand, groups with PETG had higher values. The materials that have PETG in the composition, showed, for the most part, brittle fracture. Different from the material with Polypropylene, which presented ductile fracture, in its entirety. Conclusions: The mechanical properties of thermoplastic materials used in the manufacture of orthodontic aligners should be evaluated after thermoforming. The materials with PETG showed higher elastic deformation and greater Young modules than the groups with polypropylene. Regarding the type of fracture, the composition of the plastic was also determinant in relation to the behavior of plastics under mechanical stress.