sensitivity in tooth can be due to some reasons like enamel erosion because of bruxism
, hard brushing and after the orthodontic treatment.
Use a desensitising toothpaste like thermoseal ra. Rub on the teeth surface gently for 2-3 minutes and rinse. If you dont get relief after one month then you need to go to dentist
. Doc will cover the exposed area with aesthetic restorative materials. Avoid taking too much cold and hot food.