The purpose of this study was to investigate the stress distribution and tooth displacement at the initial phase produced by 5 types of molar uprighting springs using finite element method. The three dimensional finite element model of lower dentition, bone and springs was composed of 5803 elements and 2071 nodes.
The results were as follows:
1. In case of helical spring and root spring, intrusion of lower canine and first premolar were observed and distal tipping, translation and extrusion of lower second molar were observed.
2. In case of T-loop, modified T-loop and box loop, intrusion and distal translation of lower second premolar were observed, and the largest crown distal tipping and translation of lower second molar were observed in T-loop and the smallest were observed in box loop.
3. In case of T-loop with cinch-back, crown distal tipping and translation of lower second molar were decreased, but extrusion was also decreased.
4. With increase of activation in T-loop, mesial translation and crown distal tipping of lower second molar were increased and
edentulous space was closing, but distal translation of second premolar was also increased.
5. With increase of tip-back bend in T--loop, distal tipping and translation of lower second molar were increased, but extrusion
was also increased more largely.
|