Hello to all,
Vaping is new to me but dentistry is not I have been in the field for 40+ yr. There are all kind of stains but I will limit this discussion to what is call extrinsic or surface stain. The most common types are green, , orange, yellow black and brown. The first two are almost exclusive to poor oral hygiene or as I like to say , people who don't stand in the same room as their tooth brush. The color of the 1st 2 and the last one are from an over abundance of a bacteria that is cromogenic ie produces a color as a byproduct of it metabolism.
Black or specifically black line is also a cromogenic stain which you will get even if you do not consume the traditional things that cause stain(coffee,tea,smoking and wine). Now we get to the brown which is the most common. This comes from things that are dark colored. What I would question is the staining coming from the actual e-juice vapor. I did a simple test, I covered my cartridge with a tissue and vaped several times and then looked at the tissue. No color visible on the tissue. I use 16mg dekang Mocha. Oh the things I do for science; I then took an analog Marlboro and did the same thing with a tissue, big brown spot!(No I did not inhale, yuck!) What I'm leaning more to is the dry mouth theory and not the e-juice especially if you have one of the other stain causing habits. Dry mouth reeks havoc in the mouth, cavities increase gum tissue gets red and yes stain increases. Oral tissue and teeth are designed to be kept wet.
I am no scientist. My theory is my own at this point until we get some research. Let me know what you think.