I have been using mine for just over a month now I think and I haven't had any problems. It has been used all the time except for when i am out of the house. I find that so far it hasn't done anything to my teeth. I haven't had any pain or discomfort in any parts of my teeth, jaw bone, tongue etc. Although I have now started to realise that I am addicted to it, especially at night. It is just second nature to pop it in before bed now and I don't even think about it half of the time. I was using it once a few days back for a few hours when I went to go out of the house and it was only when I seen the reflection of myself in the door window that I noticed I didn't take it out. It's comfortable and once it's in I forget its there until I see it. Sorry about the ramble but just thought I would include some extra info or an exciting read