My nti nightguard made my teeth shift. i have a underbite now and the bite is uneven. why did this happen, and what is the best treatment to fix it?

Normal risk: Nti appliances are best for short term use. Many dentists prescribe them because they are easy to fabricate and offer rapid improvement for most night time brusxing and tmd problems. Over a long period, the back teeth will shift towards the opposite arch. This will change your bite and can worsen the problems. Consider talking to a comprehensive dentist who understands bite related problems.

Not sure, discuss it: While at first glance, you might attribute 100% of your problem to the nti appliance, it might be more complicated than that. That is not to say that the nti appliance made it worse, (nor caused it). Never having seen you or your bite before and now, we can only guess as to what's going on and why. Discuss this with your dentist and consider orthodontics if appropriate.

Jaw came forward: When the jaw is pushed back in the joint from chronic clenching, eventually the teeth adapt to this position and it is forced to function there. When the bite is relieved the jaw can come forward where the muscles are relaxed. Then, only the front teeth hit. At this point the teeth need to be moved back to a position in harmony with where the muscles want the jaw to be. See an orthodontist.

NTI: This is a complex problem. I see many of these cases in my practice. Often the nti was designed wrong or used wrong. Any mandibular positioning device can and will change the bite over time. One of the ways to prevent this is to make a tooth repositioning device to be worn as well. To correct your problem i would need to correct your bite. There is more to check though.

See orthodontist: Any device held between teeth over long period of time has the potential to move them as a side-effect. Seek an opinion with an orthodontic specialist to determine what can be done to correct your occlusion and yet take caution with your jaw symptoms.

Night wear only: If an nti appliance is worn around the clock, it becomes a powerful orthodontic appliance. It is really important to just wear it part time to help avoid this.

Multiple reasons: If wrong appliance for your problem, or if appliance not worn exactly as directed. There can be unfortunate results. If appliance eliminated muscle spasm, jaw can reposition. Lots of reasons. Go see a qualified orthodontic specialist to find out 1) what's going on and 2) what can be done to rx problem.

Common with NTI: This is a common occurrence with nti. Designed to stop spasm of temporalis muscle. Better approach is to use an appliance that covers all the teeth at a scientifically determined position when the muscles are relaxed. At this point, you must do that and then see what can be done to transfer that position to the teeth permanently. No ortho until you are symptom free!

Depends: on the mouthguard. if it was over the counter and not provided by a dentist, it may indeed have pushed your teeth and created problems with your bite. I would see an orthodontist about what can be done to fix your bite. Maybe some custom aligners? I would ask them