A photoelastic study on the initial stress distribution by 3 types of molar uprighitng spring

Chun, Youn Sic

Abstract

The aim of this investigation was to identify which spring is more suitable for uprighting of the 30 degree inclined lower second molar in different situations. Between four different molar uprighting springs which were A, B, C type and T-Ioop spring, the author tested T-loop spring as a control material and the other springs were experimental group, Each spring was fabricated from .017" X .025" TMA wire and preactivated with 40 degree tip-back bend. Stabilizing unit included from the lower right central incisor to the lower right second premolar which were made by acrylic resin. The photoelastic overview of the lower right quadrant showed that stress concentrations were observed in its photoelastic model. The obtained results were as follows. 1. Higher concentration of compression can be seen clearly at the distal curvature than the mesial of the lower second molar when A type uprighting spring was applied, which can be used as a space regainer. 2. Higher level compression was presented at the mesial root apex area than the distal of the lower second molar in B type uprighting spring, which can be used as a space closer. 3. Areas of higher compression and tension were observed about the mesial and distal root of the lower second molar than A and B type in C type uprighting spring, which can be used as a partial space regainer.