What causes sensitive teeth?

Nerves in teeth: The nerves in teeth are responsible for pain sensation. There are many reasons why the nerves respond to different stimuli. Range can be from deep cavities to abrasion at the gum line to bruxing/grinding to name a few.

Brushing too hard: Few things can thinout the enamel or break it causing exposure of the second layer or dentin. When dentin is exposed lots of sensitivity is experienced specially to light touch and air or cold air or water. Thinning or abrasion of enamel is caused by 1. Brushing too hard, 2. Using a hard brush 3. Grinding of teeth causing chipping of enamel at the gum area.

Many reasons: From deep cavities/fillings to grinding to fractures, etc. Most common cause, however, is gum recession exposing roots of the teeth to the oral environment. Ask your dentist if a consultation with a periodontist is in order.