extractions for invisalign

[happysmile]

is it true that if you have extractions, that you have to extract in even numbers? for example, the least you can extract on top and bottom is 2 for each; and if you extract two on top, you must extract 2 on bottom?

[Sunny]

No this isn't true.

You can have any number of extractions and they don't need to be the same on the lower and upper. Some people have one tooth removed, some two, some three and some four. It's all about removing the amount needed so that the space made is sufficient to correct the alignment and bite. If only a little extra space is needed, no teeth need to be removed and instead a small amount can be shaved from some of the exisiting teeth ... this is called IPR.