Dentist only: sharp pain runs up back of front tooth less than 1 sec. at a time for 2 days but not often. use night guard. checkup xrays dec. perfect. not loose. no gum prob. xrays good. root exposed?

Jaw Joint Aclamation: If someone who wears a night guard appliance is clenching or grinding more severely than usual, lubricants can be forced out of the joint causing the bite to feel off in the morning when the appliance is removed. Additionally, arthritic changes in the joint can do the same thing. Have an evaluation by the dentist who fabricated your night guard.

Possibly...: What causes the sharp pain? Has the tooth been checked for vitality? Are there any restorations on the tooth, or hx of root canal therapy? Hard to give you meaningful advice without these answers and seeing the tooth and film(s). There may be a hairline fracture. Please get a second local opinion. All the best...

Root sensitivity: If all xrays are clear. Then most likely your symptoms are coming from exposed roots causing sensitivity to occur. Most patients that experience root sensitivity describe it as an "electrical" shock. Several options: 1) use a toothpaste that is designed for sensitive teeth like sensodyne. 2) bonding over the roots to cover the exposed areas. 3) laser therapy on the roots. Check with your dentist.

Differential Dx: Could be atypical facial pain, irreversible pulpitis, ligament stress based on night guard wear/non-wear, fractured root, exposed root, or post-trauma reaction.