수종의 교정용 탄성 체인의 하중-변위 특성과 응력 이완의 비교

Abstract

The purpose of this study was to investigate the effect of extension speed on load-deflection characteristics of elastomeric chains, and stress relaxation of elastomeric chains during uninterrupted extension of 4 weeks. Gray and transparent elastomeric chains from Ormco, 3M Unitek, RMO were tested. For load-deflection test, elastomeric chains were extended 10 mm (102% to 105% extension) with two extension speed of 10 mm/sec and 0.1 mm/sec. For stress relaxation test, the elastomeric chains were extended 10 mm and maintained on the force gauge for 4 weeks. The results were as follows. 1. When the extension speed was lowered to 0.1 mm/sec, forces during both extension and unloading significantly decreased, and the permanent deformation significantly increased. 2. The initial force of elastomeric chains decreased 23% to 48% during initial 12 hours of constant extension, and then decreased 8% to 11% more during the rest of 4 week period resulting in 31% to 59% loss of initial force. 3. After 4 week of constant extension, the remaining force was 69% in RMO gray chain, and 67% in RMO transparent chain, 60% in both Ormco gray and clear chains, 50% in Unitek transparent chain, and 41% in Unitek gray chain. In conclusion, it is recommended to use RMO chain which has shown minimal stress relaxation. And also, initial force level of elastomeric chain can be determined considering the stress relaxation pattern revealed in this study.