PHOTOELASTIC STRESS ANALYSIS OF DIFFERENT MOLAR UPRIGHTING SPRINGS

The aim of this study was to analyze and compare the stress distributions in three molar uprighting techniques: cantilever, uprighting spring and Sander’s Spring, using quantitative and qualitative photoelastic analysis. Seven photoelastic models were made, the second molar was tipped forward 30º and the mandibular right canine and the first and second premolars were the anchor teeth. In each of the photoelastic models, we tested uprighting mechanics randomly. A software Fringes® was used to quantify the model’s shear stress. In the quantitative analysis the nonparametric Kruskal-wallis test demonstrated that only one point of the 18 analyzed, presented statistically significant difference, on point 14 (P=.033). The Post hoc Dunn’s test showed difference between cantilever group and the group Sander's Spring bended 135°. In the qualitative analysis, the highest concentration order of isochromatic fringes was on point 6 of the molar. There was no statistically significant difference in all molar points. On anchor teeth the Sander’s Spring bended 135º presented higher values on the order of fringes. With the results obtained in this research, the clinical decision of which mechanism of verticalization to use will be a personal preference of the orthodontist.