Hi Isobelj,
An anterior open bite means that your front teeth don't meet, and a posterior open bite means that your back teeth don't meet.
I had always had a very slight anterior open bite, but after I used an NTI, it opened more. I have since had it closed more with crowns. I couldn't close it all the way because it would have looked like I have rat teeth.
One of the problems with an anterior open bite is that it is very difficult to bite through food. Also, if your grind your teeth at night, the lack of canine guidance could mean that all the force is directed on the molars. Having all the force so close to the joint can put more strain on it than if the force were directed more anteriorally. I still wear my NTI at night so it is kind of like having canine guidance.
I have been told (and I believe it) that through use of NTI, my muscles became more relaxed and allowed my condyles to move into a more stable position. Unfortunately, I think that for about 5% of us that use NTI, the bite opens.
Having the condyle reposition is in itself not enough to help me. I believe it has been helpful in that I have less clicking, but my pain is primarily muscular. In order to control that pain, I have to keep wearing my NTI.
I don't know how long it takes on average for a bite to open in splint therapy. It happened gradually for me. I also don't know how long you have to wear the splint before the change is permanent. Bone is a dynamic tissue and remodels itself, so I know I have had some changes that could not be easily reversed.
I hope this helps.
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