橡皮圈
2.Many soldiers got the idea of making life preservers out of straw, because the rubber ones would deflate if short. 
3.Results: The research discovered elastomenc ligatures and elastomenc chain are biggest in the experimental initial 48 hour internal stress weaken, after load 48 hours remaining stress for about initial stress 80%.
4.4 Wear ligating modules,headgear and other accessories as instructed by your orthodontist.
5.Methods: The randomly selection elastomenc ligatures, elastomenc chain and nickel titanium coil springs each nine, each kind of goods randomly divide into three groups, each group of three, every group goods distinction load 100 gram, 150 gram and 200 grams.
