This is very difficult to answer without more information from a dental exam. X-ray is needed along with a physical examination of the area. Sometimes the gums around the crown can be very inflamed causing some of the bleeding. There is a chance that the root is fractured too. But it is difficult to make that diagnosis without more info. Also I find that most crowns and post come out for a reason and probably 9 out of 10 has to do with recurrent decay around the crown.
Many times the seal between the teeth and gums when doing in office bleaching will leak. If you get the bleach on the gums it will "burn" them. Most of the time it is just uncomfortable for a few days and always does away. If you are very concerned go back to the dentist who did the bleaching to have it looked at. They might be able to give you some topical medication/ointment to relieve the pain and improve healing.
It is not uncommon to have to remove a few teeth when considering orthodontic appliances such as Invisalign. The most common teeth removed are the premolars. This allows for more space to move teeth especially in severely crowding teeth cases. Sometimes by not removing the teeth the end result will be unsatisfactory.
First of all I would agree with Dr. Timmerman. Not only do I do a diagnostic wax up for all "cosmetic" cases, many times I will have the lab fabricate the temporary crowns based off the wax up. Using a diagnostic wax up is going to allow you to view how your teeth should look and when you are satisfied you can give the go ahead. I try to make as cosmetic a temporary as I can that way I know the gums will heal properly and the outcome will be as aesthetic as possible. When doing cosmetic work, cheaper is not always better...
Replacing a sealant is a lot better then having to replace a filling. It sounds like your teeth did very well with sealants. I would continue to protect them by replacing the sealant.
