Unfortunately once you have crowns you cannot go back to veneers, but All Porcelain Crowns can look as good as veneers if the are done well. Many of the cases that I do are combination cases with crowns next to veneers and you cannot tell which tooth was treated with a veneer or a crown. What you have to realize is that the tooth structure underneath the crown or veneer will severely influence the final look of the crown or veneer. If we are trying to make a significant color change for dark stained teeth the porcelain will need to be more opaque and not as transparent. You may have a difficult case to treat. Find a cosmetic dentist on AACD.com and get a second opinion. Sorry for your trouble.
The correction of a gummy smile in combination with porcelain veneers can look amazing when done well. There are several ways to handle this case and I would recommend that your cosmetic dentist work with a periodontist (gum surgeon) to plan the case together. When I do these cases I will plan the final length of the teeth and make a guide for the gum surgeon to remove the right amount of gum tissue. As far as the healing time needed before the veneers are bonded in it will depend on how the surgery is performed. The consensus in the dental literature is that you can take your final impression for the veneers when there is a probable sulcus. This means when the tissue and gum pocket is healthy. A rough estimate would be six to 8 weeks. During this healing time my patients will wear a prototype of their final veneers that looks very nice and give both of us a chance to evaluate the esthetics. Good luck!! Send me before and after pictures of your case.
The bonding of veneers onto teeth is a very technique sensitive procedure and if not handled properly can lead to bacterial micro leakage. Micro leakage can cause dark staining at the gumline. It sounds like your second opinion was accurate in her descriptions. Unfortunately if this is the case the veneers will need to be redone. If you send me close up photos of these grey areas I can give you more information. I hope that helps.
Invisalign is not designed to use with headgear. Unfortunately it doesn't look you are a good candidate for invisalign. You have what is called a Class III biting arrangement. Your lower teeth are forward of your upper teeth. From this one picture it looks as if your teeth are in good position and that your lower jaw is forward. I would say that you have a Skeletal Class III Occlusion (bite) which is not treated with orthodontics alone and would require jaw surgery. Consult with your orthodontist and oral surgeon as to the best treatment option for you. These cases can look great after surgery and you should ask for before and after photos of similar cases to yours. Good luck with you treatment.
You should not need to wait an extended length of time to whiten you teeth after brusing. It is recommended that the teeh be clean and free of plaque and tarter for the best results.