Got some dual coils a short while back and started using them. Liked the clear 1.5's the best as they seemed to work better than the other black ones but did use both. a few days after using them i got what the dentist said was a kanker sore inside my mouth and the place it was at just hurt like hell. Ive never had one of these in my life and never wanted another. After about 5 days it went away but i could feel another one coming on on my tongue and another on my inside top lip. I was at the beach on vacation now it this was really messing up my eating out and enjoyment as it made my whole mouth hurt. It did not click until the end of my vacation week that the only thing i had changed was using the dual coils because i wasnt eating or drinking anything different than usuall. So i stopped using them on friday of last week and the sores i had have cleared up today monday and no new ones are coming up that i can tell. So i will definately be trashing these cartos. It really sucks to because i really liked them and their performance. Whats really weird though is that No other cartos have ever done this, guess its back to the regular boges for me though. Anyone else ever had a problem like this and if it ever happens to you now you know what could be causing it.