Effects of prestretch on stress relaxation and permanent deformation of orthodontic synthetic elastomeric chains
Chang Jee-Hae, 황충주, 김경호, 차정열, 김광만, 유형석,
소속 상세정보
( Chang Jee-Hae ) - Yonsei University College of Dentistry Department of Orthodontics
황충주 ( Hwang Chung-Ju ) - Yonsei University College of Dentistry Department of Orthodontics
김경호 ( Kim Kyung-Ho ) - Yonsei University College of Dentistry Gangnam Severance Hospital Department of Orthodontics
차정열 ( Cha Jung-Yul ) - Yonsei University College of Dentistry Department of Orthodontics
김광만 ( Kim Kwang-Mahn ) - Yonsei University College of Dentistry Research Institute of Dental Biomaterials and Bioengineering
유형석 ( Yu Hyung-Seog ) - Yonsei University College of Dentistry Department of Orthodontics
Abstract
Objective: This study was performed to investigate an appropriate degree of prestretch for orthodontic synthetic elastomeric chains focusing on timedependent viscoelastic properties.
Methods: Orthodontic synthetic elastomeric chains of two brands were prestretched to 50, 100, 150, and 200% of the original length in one and three cycles, and the hysteresis areas of the obtained stress-strain curves were determined. Acrylic plates were employed to maintain constant strain during the experiment. A total of 180 samples were classified into nine groups according to brand, and their stresses and permanent deformations were measured immediately after prestretch (0 hour), after 1 hour and 24 hours, and after 1, 2, 3, 4, 5, 6, 7, and 8 weeks. The relationship between stress relaxation and permanent deformation was investigated for various degrees of prestretch, and the estimated stress resulting from tooth movement was calculated.
Results: The degree of prestretch and the stress relaxation ratio exhibited a strong negative correlation, whereas no correlation was found between the degree of prestretch and the average normalized permanent strain. The maximal estimated stress was observed when prestretch was performed in three cycles to 200% of the original length
Conclusions: Although prestretch benefited residual stress, it did not exhibit negative effects such as permanent deformation. The maximal estimated stress was observed at the maximal prestretch, but the difference between prestretch and control groups decreased with time. In general, higher residual stresses were observed for product B than for product A, but this difference was not clinically significant.
키워드
Orthodontic synthetic elastomeric chain; Prestretch; Stress relaxation; Permanent deformation
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