Mousavi Seyed Mohammad, Mahboobi Sara, Rakhshan Vahid
Department of Orthodontics, School of Dentistry, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Dentist in Private Practice, Tehran, Iran.
Dent Res J (Isfahan). 2020 Sep 7;17(5):326-337. eCollection 2020 Sep-Oct.
Elastomeric chains are of clinical importance to orthodontics. Therefore, their behavior should be assessed under different conditions. Some of their critical aspects remain unstudied (including effects of different elongations and chain forms on their force properties). Therefore, we aimed to assess these factors.
This study was performed on 540 observations: first, 90 chains (10 specimens per subgroup of three brands [American Orthodontics, Ortho Technology (OT), and G&H], each from three chain types [closed, short, and long]) were stretched for three extents (40%, 60%, and 100%) and their forces were measured using a universal testing machine. Afterward, 270 new chains of the same brands/types were stretched for the same extents by installing them onto pairs of pins with different interpin distances. Plates holding pins/chains were incubated in artificial saliva at 37°C for 4 weeks. Afterward, their forces were measured and analyzed using partial correlation coefficient, three-way analysis of variance (ANOVA), Tukey, Student's t, and Mann-Whitney tests (α = 0.001).
Forces degraded significantly from an overall mean of 3.97 ± 0.97 N to 1.29 ± 0.39 N after 4 weeks (all = 0.000, -test/Mann-Whitney). ANOVA showed highly significant differences among brands, types, and elongations, in terms of "initial force, force decay, and residual force" (all = 0.000). Almost all post hoc pairwise comparisons were significant (Tukey = 0.000). There was a strong positive correlation between elongation extent and force loss (r = 0.846, = 0.000).
OT might be the most preferable brand. Closed chains might usually show better results, especially in OT chains. Instead of using chains half of the size of the space (to elongate for 100%), longer chains should be used to stretch for lesser extents.
弹性链在正畸学中具有临床重要性。因此，应在不同条件下评估其性能。其一些关键方面仍未得到研究（包括不同伸长率和链形式对其力性能的影响）。因此，我们旨在评估这些因素。
本研究共进行了540次观察：首先，将90根弹性链（每个品牌[美国正畸、正畸技术（OT）和G&H]的三个亚组各10个样本，每种链有三种类型[封闭型、短型和长型]）拉伸至三种程度（40%、60%和100%），并使用万能试验机测量其力。之后，将270根相同品牌/类型的新弹性链安装在不同销间距的销对上，拉伸至相同程度。装有销/链的板在37℃的人工唾液中孵育4周。之后，测量其力，并使用偏相关系数、三因素方差分析（ANOVA）、Tukey检验、Student's t检验和Mann-Whitney检验进行分析（α = 0.001）。
4周后，力从总体平均值3.97±0.97 N显著下降至1.29±0.39 N（所有P = 0.000，t检验/Mann-Whitney检验）。方差分析显示，在“初始力、力衰减和残余力”方面，品牌、类型和伸长率之间存在高度显著差异（所有P = 0.000）。几乎所有事后两两比较均具有显著性（Tukey检验P = 0.000）。伸长程度与力损失之间存在强正相关（r = 0.846，P = 0.000）。
OT可能是最优选的品牌。封闭链通常可能显示出更好的结果，尤其是在OT链中。不应使用空间尺寸一半大小的链（伸长100%），而应使用较长的链以较小的程度进行拉伸。
