Possible Solutions for crowded teeth instead of premolar extractions?

I'm thirteen and had braces since the 4th grade. So basically it's been a good three years of braces. I took them off last summer but they aren't completely straight. I asked my ortho about it and he said that the only way for my teeth to be completely straight is for me to get my premolars extracted. He said that way, I wouldn't have to take out my wisdom teeth later on in life. And it would be cost free except for the surgery of course. But i've been reading really negative comments about premolar extractions online and would like to know your opinion. Is there any possible solutions for crowded teeth instead of premolar extractions? I heard expanders are only for cross bites. And I don't want surgery. Please help!