Premolar extraction for braces? (photo)

You are absolutely correct. Extracting only one premolar would leave your midline (contact point between your upper two front teeth) off centered from your face. I would STRONGLY recommend that you not have ANY teeth removed. Your problem is obviously overly crowded teeth but it's not because you have too many teeth, it's because your upper jaw is underdeveloped. Your orthodontist is thinking only of straightening your teeth which would be very easy to do by extracting a single tooth because this would give you the necessary space to align the remaining teeth. However, this would do nothing to address the real cause of your crooked teeth which is a narrow dental arch. Before any teeth are ever moved you should understand what effect that will have on your facial aesthetics, TMJ health and your airway. If you extract one bicuspid you will always have dental arches that are too narrow, you will have a midline that is off center from your face, you will have overly retracted upper front teeth, you will potentially have TMJ problems, you will potentially have sleep disordered breathing, and you will always have a narrow smile. These are just the obvious ramifications. Find a doctor who understands the relationship between tooth movement and facial aesthetics, TMJ health and airway health. Don't settle for treatment from anyone who can't speak intelligently about all three of these incredibly important issues before you ever move a single tooth, much less PERMANENTLY remove a tooth from your mouth.Your problem of an underdeveloped upper arch can be easily resolved with the use of a simple and comfortable removable appliance.Good luck!

You are correct that premolars are normally extracted bilaterally. This is because a bilateral problem requires bilateral extractions to remain symmetrical. If however your initial problem is very asymmetric then asymmetric extractions (just on one side) can sometimes be done.The photo you provided shows relative symmetry of your front teeth but I have no idea what is going on in the back so I cannot say if your treatment plan is correct