Re: front tooth hurts
I don't know if this will help at all, but I also wore a nightguard to help prevent grinding my teeth. At first I had no problems and it fit well. It was a hard nightguard custom-made by my dentist. Over time, however, my teeth shifted and I began to get severe pain in two particular teeth. It was like you described - a pressure-like pain. Fortunately mine stopped when I stopped using the nightguard. Perhaps your mouthguard was not a good fit. Have you stopped using it?
On an unrelated note - like the poster above I also had severe pain in two lower molars that just would not quit (not the teeth bothered by the mouthguard). I too was diagnosed with a neuralgia of the trigeminal nerve and take medication to help control (but not stop it). I had seen multiple dentists and endodontists before this to try to figure out where the pain was coming from. My condition was diagnosed with an MRI. Sorry, I don't know if a CT scan can do this. Best wishes!