Bonding would work...
I would recommend veneers, but since this is something that you definitely do not want, I would recommend getting bonding. Bonding will accomplish the goal of closing the triangles and preventing cavities from invading. However, if you get bonding, you can expect to need the dental bonding to be re-done several times over the course of the next several years. Bonding stains very easily and does not last nearly as long as your natural teeth. Good luck and I hope this helps. Follow me if you have more questions.
Sarah Thompson, DMD
Can bonding done to close a tooth's black triangle always produce a ledge that later results in a cavity?
If properly done, and you have good oral hygiene, direct composite bonding used to close the black triangles where your gums have receded, should not result in cavities later on. However, please note that your cosmetic dentist will have much better control over closing the space of the black triangle and giving your normally shaped and proportioned teeth with porcelain veneers.