Interarch elastic bands are longer than braces ligatures and are used to help fix a misaligned bite. The Braces Guide explains how interarch braces attach to small hooks on braces brackets, forming a stretchy connection between the upper and lower teeth. As well as improving the way patients' teeth fit together, orthodontists use interarch elastics for other purposes like closing spaces between teeth.
You might hear your orthodontist refer to the "class" of interarch elastics. Class II elastics help correct an overbite, where the upper teeth sit too far forward. Class III elastics correct an underbite, where the lower teeth are too far forward in the mouth.
Interarch elastics are available in different lengths to fit the size of the gap between the upper and lower bracket hooks, exerting the correct amount of pressure but allowing a patient to open their mouth comfortably to speak. When the elastics are adjusting a misaligned bite they must generally be worn all the time except when eating or brushing your teeth. However, if the elastics are only needed for light maintenance, then the orthodontist may only prescribe nighttime wear.
It's the consistent tension on the teeth and jaw that makes interarch elastics effective. If the patient doesn't wear their elastics as prescribed, the treatment time is lengthened. Wearing two elastic bands as an alternative to wearing the bands consistently isn't an effective alternative, says the Braces Guide. Doubling up interarch elastics can increase soreness and even make treatment time longer if your teeth move in an unintended way.