Why patients feel sensitivity suddenly after breakage of front less than half tooth and after a day sensitivity starts to go?

Exposed dentin: Microstructure of dentin includes tubules that lead straight to the pulp (the nerve). Dynamic fluid movement in and out of tubule causing sensitivity and hyperemic pulp reaction. Breakage of enamel exposed the dentin to oral fluid and sets off this situation. Go to your dentist to fill and seal this exposed dentin. Moreover, the trauma may kill the nerve, which require follow ups to rule out.

Broken tooth infect: A healthy tooth has a nerve inside of it and when the tooth breaks, the nerve becomes exposed and can be quite painful. As the time of the exposure continues, the internal portion of the tooth, the pulp, dies and the pain may subside. But don't be fooled, it is not ok! serious infection will ensue. This infection can and will begin to travel. Don't ignore a broken tooth, w or w/o pain!