Vapor on the lungs is significantly less harmful than smoke, but it still is known to irritate the lungs in many users (such as myself). I am not highly educated in the exact science of how and why it irritates, but it does, and irritation is your body reacting to something adversely affecting it... vape juice flavors/different mixtures I am sure definately affect the harm done. I have had different juices, some cause a terrible itch in my throat, while others stay smooth and never really irritate with moderate use. As far as how it effects your teeth, I bet it does. To what extent? Sadly scientists haven’t studied that much. I’m sure anything that goes in your mouth effects your teeth.. if your vaping a pretty natural juice, versus shit with tons of chemicals, you probably won’t see a huge impact or discoloration on your teeth, particularly if you are a mellow user. I am a mellow vape user, have been for almost 5 years, only vaping credible and revered juices, and I have not noticed any discoloration or issues in my teeth/ skin/ lungs. Again, keep in mind, I believe a lot of that is attributed to my moderated use. I’m sure over doing vaping can still show adverse affects in all the areas you mentioned.