Highly doubtful that anyone will read this far into this post since the topic has changed multiple times. To the OP, I was agreeing with you that I have experienced the same situation. First on the Crown 3, then the smok, etc. So my Sense Screen tank just started leaving a black film (that bushes off) on my front teeth. I looked at the coil and it looked really really black. What my conclusion was is that the coil began to get slightly burnt due to the installed time and then when I hit the vape it would spit small bits of burnt juice that would hit my teeth.
So my recommendation is to change your coil and see if it goes away. That may be your deciding factor in coil changes. I don't think I would go vegan or whatever the rest of these people are talking about. I also believe you have a decent oral hygiene regimen so that isn't an issue either.
So my recommendation is to change your coil and see if it goes away. That may be your deciding factor in coil changes. I don't think I would go vegan or whatever the rest of these people are talking about. I also believe you have a decent oral hygiene regimen so that isn't an issue either.