Miniparafusos ortodônticos aplicados em tratamentos de deformidades dentofaciais

Abstract

In an orthodontic treatment, there are several factors that can influence your prognosis, among which anchorage, which in general is a challenge for orthodontists, stands out. Miniscrews comprise one of the main innovations and technological advances in orthodontic clinical practice because they have the ability to perform absolute anchorage. There are currently available in the national and international market a series of miniscrews, with different shapes and sizes, made of titanium alloy, and steel. Currently, some types of deformities can be treated by skeletal anchorage using orthodontic miniscrews on thicker cortical bone structures and in extra-alveolar positions. Often, they represent a good alternative to miniplates. However, this type of anchorage requires the application of relatively high forces compared to other types of orthodontic treatment, associated with insertion torques at different angulations. These associations, in general, can lead to miniscrew failure. Therefore, an understanding of the biomechanics of this type of extra-alveolar fixation can define the design of miniscrews optimized for an effective treatment of deformities by means of skeletal anchorage. The aim of this work is to evaluate and compare steel and titanium miniscrews, normally used for extra-alveolar anchorage, observing the real capacity to support the forces and torques generated in the extra-alveolar bone insertion for the therapy of total retraction of the inferior and superior dento-alveolar complex, since titanium miniscrews are not designed and manufactured for this purpose, not supporting well these insertions, as well as to design an optimized orthodontic miniscrew. The following tests were performed: 1) "In Vitro" tests on pig mandibles comparing the insertion of stainless steel (gold standard) and titanium (2.0 x 12 mm) mini screws, also evaluating miniscrews with smaller diameter and length; 2) Strength analysis of stainless steel and titanium miniscrews by means of insertion in different angles in high density cortical bone (synthetic blocks); 3) Numerical modeling by finite elements aiming to evaluate the resistance of conventional steel and titanium miniscrews (Dr. Chang model) and optimization process with different miniscrew models proposed for extra-alveolar fixation; 4) Applicability of stainless steel miniscrews (gold standard) in extra-alveolar position in class II treatments - Total maxillary retraction; 5) Applicability of stainless steel miniscrews (gold standard) in extra-alveolar position in class III treatments - Total mandible retraction. The development of a new miniscrew model aims to reduce structural failures, reducing costs with greater comfort and rehabilitation in a shorter time for treatments of deformities with the use of extra-alveolar insertion.