What Does It Mean If The “center Line” Of Your Teeth (top And Bottom) Doesn’t Match?

I just started invisalign to straighten my teeth, but I’m doing express, which means its only for 5 months. The animation they showed me shows that my teeth will be straight when I’m done, but the center line (space between two top and two bottom teeth) won’t be exact. It will be improved, but not equal. The orthodontist told me it shouldn’t affect anything and was purely cosmetic. Also, he said fixing that would call for a much longer treatment and more $. So I’m perfectly fine with it as long as my teeth are straight, but what does that alignment mean?

Dental Hygenist Recommends Expander, Insurance Doesnt Cover Ortho? ?

I saw my dentist for the first time in 5 yrs(had no health insurance) and actually he wasn’t in so I saw his terrible dental hygenist she took x-rays/cleaned/examined..came out with a bunch of cavities(not sure of the # she said he might find more?) which doesn’t bother me, because genetically I’m pretty prone to them..She also mentioned I go back to my orthodontist(havent seen him in about 5 years also…) and get an expander on the bottom of my teeth if I could..(I have overcrowding since my wisdom teeth came in/not wearing my retainer..dammit.) Well here’s my issue, my dental insurance doesn’t cover orthodontics(wonderrrful..) and I’m not exactly rich(more like starving college student, whom mommy & daddy havent loaned me a penny since I was 13..) and I don’t know what to do..I’ve made the appointment with the orthodontist to get a permanent metal bracket on the back of my two front teeth put back on..(if he can, that happened almost 2 years ago)..and I don’t want to mention the expander and have him start doing things and not be able to pay my rent this month..What should I do? If I don’t get this expander, will my dentist just stop seeing me?