Evaluation of tensile strength of different configurations of orthodontic retraction loops for obtaining optimized forces

The aim of this study was to analyze the mechanical behavior of different orthodontic retraction loops. Two designs of orthodontic loops for closing space were analyzed: teardrop-shaped (T) and circle-shaped loop (C), of two different heights (6 and 8 mm), and two types of orthodontic wires (stainless steel – 0.19 ’ × 0.25’; TMA – titanium molybdenum alloy – 0.016 ’ × 0.016’). The sample consisted of 80 loops, divided into 8 groups determined by the combination shape/height/type of wire, which were submitted to tensile testing at a speed of 2 mm/min., to measure the quantity of force generated when activated in the interval of 0.75 mm and 2.25 mm. The results were submitted to the ANOVA and Tukey statistical tests to com-pare the groups, and the Student’s-t test to compare the means of two groups. Statistically higher values were observed for the size 6 mm, circle shape and stainless steel composition. The group “teardrop-8 mm-TMA ” together with the group “circle-8 mm-TMA ” presented the lowest mean value, differing sta-tistically from all of the other groups. It was concluded that the alloy of the wire and the height of the loop would be more important than the loop design