You may have a malocclusion - meaning that your bite is off. When you close your mouth, do your front bottom and front top teeth touch? That is what was causing my top front teeth to become loose. It was also causing sensitivity in those top teeth and the daily trauma of the bottom teeth pressing the top teeth forward finally caused me to need a root canal. I am now, at the age of 40, wearing braces to correct this problem. The sensitivity has cleared up. It is too soon to know if the loose teeth problem is solved, since braces are constantly shifting the teeth about anyway.