I have linguals on 8 front teeth in the top as well as the bottom. I've had them on since August 5th and already, by the time October hit i could see huge HUGE improvements in my smile. Until, I went to the dentist for a change of wires, during that visit he used this machine to make a few spaces in my teeth so that they can move easily, i believe is called "reprox?". He also put in a new wire called "mushroom?" as well as piece of thread (possibly made of rubber?)... anyhow. So, the next day I wake up and i was amazed at how good my teeth looked, and then the next day i wake up and a tooth shifted outward. Meaning now it pops out, it looks terrible, I can't wait until my next appointment to see what he does about it.
So now myquestions to you guys is, did things look really bad before they looked good? If so, why do u think this happens?
Thanks in advance, i'll post a pic tonight of my teeth, right now I'm at work (shhh)
Sounds like you've had interproximal reduction - stripping of some of the enamel between teeth.
Things do tend to get worse before they get better. I guess it's like unscrambling a rubik cube; you have to move stuff around into what seems like unlikely positions before it all comes together at the end.
My experience with the a tooth coming out of line and a other aspects of things getting worse before they get better is that it's not harmful and will all get sorted in the end. However it is not always necessary either, my ortho has fixed everything I mentioned quickly, so if it bothers you go back and ask about it. For me having paid a lot for an invisible brace there seems little point in going around with uneven teeth if this is not necessary
amazed at how good my teeth looked, and then the next day i wake up and a tooth shifted outward. 
Meaning now it pops out, it looks terrible, I can't wait until my next appointment to see what he does about it. 