to seek second opinions. Usually they all have first estimate sessions free or small charges.
I don't think you should let this (磨掉三分之一) happen. It won't be good to the teeth, but I am not a dentist or a doctor. When my son had to do 牙齿矫正, I tried three orthodontists, two of them said he had to have two teeth pulled out. I chose the one who said no need to pull the teeth or do any damage to the teeth. Now he is all done with 牙齿矫正 and has a beautiful full mouth of teeth.