Elastic chain is not recommended for closure of large spaces, because of force level issues. For example, 'C-l' chains stretched from first molar to first molar, initially generate 400 gm of force in the upper arch and 350 gm of force in the lower arch. This places them in the force range just below closing loops and steel Fletcher coil springs. In a first premolar extraction case, for example, over-stretched chain links in the extraction sites (Fig. 9.13) will cause rotation of adjacent teeth. Under-stretched chain links in the extraction sites (Fig. 9.14) will not produce any space closure.
Flastic chain is useful for dealing with one or two minor spaces towards the end of treatment (p. 295) and light chain can be helpful in preventing spaces from opening late in the treatment, when finishing .014 wires are in place.
Fig. 9.13 Over-stretched elastic chains can cause unwanted rotations.
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