School of Stomatology, Zhejiang Chinese Medical University, Hangzhou, China.
Department of Orthodontics, Zhejiang Chinese Medical University affiliated Stomatology Hospital, Hangzhou, China.
Am J Orthod Dentofacial Orthop. 2020 Mar;157(3):313-319. doi: 10.1016/j.ajodo.2019.03.028.
The objective of this study was to evaluate the characteristics of force degradation of latex elastics of 10 kinds of elastics over 48 hours, both in vivo and in vitro.
For the in vivo study, 10 different kinds of elastics were randomly chosen for investigation: 1/8-inch (2 oz); 1/8-inch (3.5 oz); 3/16-inch (2 oz); 3/16-inch (3.5 oz); 1/4-inch (2 oz); 1/4-inch (3.5 oz); 5/16-inch (2 oz); 5/16-inch (3.5 oz); 3/8-inch (2 oz); and 3/8-inch (3.5 oz). Ten volunteers (aged 22-24 years) were selected to wear personalized clear retainers, which were made to hold the elastics in the mouth and stretched to a specific length. Control samples of 1/4-inch (2 oz) and 1/4-inch (3.5 oz) latex elastics were stretched to the same length and held in dry air conditions (temperature = 25°C) and in artificial saliva (temperature = 37°C, pH = 6.7). Force value and percentage of force degradation were estimated 10 times over a 48-hour period in both the in vivo and in vitro groups. A 1-way ANOVA and t test were used to identify statistical significance (P <0.05).
The force degradation of the latex elastic in vivo is greater than in vitro. In the in vivo groups, during the first hour, the extension rate of all elastics decreased sharply about 13.16%-18.79%, then the rate of force degradation declined. The degradation of initial force was about 29.35%-39.94% after 48 hours. The extension range of 2.0-oz elastics reduced less than that of the 3.5-oz elastics in vivo. At the same time, with the same initial force, elastics with larger inner diameters decreased more slowly than the smaller elastics (P <0.05).
The force degradation of latex elastic in vivo is much greater than that in both air and artificial saliva. In vivo, the force value of the orthodontic latex elastics decreased sharply in the first hour. The larger the inner diameter and smaller the setting force value were, the slower the force decay.
本研究的目的是评估 10 种橡皮筋在 48 小时内体内和体外的力降解特性。
对于体内研究，随机选择 10 种不同类型的橡皮筋进行研究：1/8 英寸（2 盎司）；1/8 英寸（3.5 盎司）；3/16 英寸（2 盎司）；3/16 英寸（3.5 盎司）；1/4 英寸（2 盎司）；1/4 英寸（3.5 盎司）；5/16 英寸（2 盎司）；5/16 英寸（3.5 盎司）；3/8 英寸（2 盎司）；和 3/8 英寸（3.5 盎司）。选择 10 名志愿者（年龄 22-24 岁）佩戴个性化透明保持器，该保持器用于在口中固定橡皮筋并拉伸至特定长度。控制样本为 1/4 英寸（2 盎司）和 1/4 英寸（3.5 盎司）乳胶橡皮筋，拉伸至相同长度，并在干燥空气条件下（温度为 25°C）和人工唾液中（温度为 37°C，pH 值为 6.7）。在体内和体外组中，在 48 小时内每 10 次估计力值和力降解百分比。使用单因素方差分析和 t 检验来确定统计学意义（P <0.05）。
体内乳胶橡皮筋的力降解大于体外。在体内组中，在第一个小时内，所有橡皮筋的伸长率急剧下降约 13.16%-18.79%，然后力降解率下降。48 小时后，初始力的降解约为 29.35%-39.94%。2.0 盎司橡皮筋的延伸范围小于体内 3.5 盎司橡皮筋。同时，在相同的初始力下，内径较大的橡皮筋比内径较小的橡皮筋降解速度较慢（P <0.05）。
体内正畸橡皮筋的力降解明显大于空气和人工唾液中的力降解。在体内，正畸乳胶橡皮筋的力值在第一个小时内急剧下降。内直径越大，设定力值越小，力衰减越慢。
