COMPARAÇÃO DA EXPRESSÃO DO TORQUE ENTRE AS DIFERENTES LIGAS METÁLICAS: NITI, TMA E AÇO INOXIDÁVEL, EM BRÁQUETES AUTOLIGÁVEIS E CONVENCIONAIS LÍLIA DUARTE AGUIAR Dissertação apresentada à Faculdade de Odontologia das Faculdades Ingá, como parte dos requisitos para a obtenção do título de Mestre em Ortodontia. Orientador: Prof. Dr. Rodrigo Hermont Cançado Co-orientador: Prof. Dr. Ricardo Gobbi Oliveira MARINGÁ 2013

Abstract

Introduction: This study compares torque expression between three diferente metallic alloys: stainless steel, beta-titanium (TMA), and nickel-titanium (NiTi) wires in metallic self-ligating and conventional brackets. Material and Methods: In the experiment, one hundred wire segments 0.019’’ x 0.025’’ of each metallic alloy were torqued. An automated mechanism was developed to twist the wire segment, using angulations of 12o, 24o, 36o, and 48o in both conventional and self-ligating bracket systems, and torque moments were gauged through a universal testing machine (EMIC DL2000). The one-way ANOVA was used to evaluate those torque moments for each metalic alloy; the brackets sistems were compared using independent t-test; and the linear regression was used to estimate the effect of angulation on the torque moment observed on both convencional and self-ligating brackets. Results: Results show that there is a statistically significant difference in terms of the torque expressed among the three metallic alloys; stainless steel transmits the greatest moment for all angulations while NiTi expresses the lowest on both bracket systems used. Conclusion: Stainless steel alloy transmits more torque when compared to both TMA and NiTi, resulting in a better way of controlling dental inclination in orthodontics practice. For stainless steel alloy and NiTi wires, if bracket system is conventional or self-ligating is irrelevant because the expression of the torque is similar, with no statistical significance in the results, but the TMA wire generated torque moment larger in self-ligating sistem , this fact can be explained by the smaller size of the slot Damon MX compared to Roth Max.