The sensitivity of teeth is a result of the receding gum line which exposes the underlying dentin. When the underlying dentin becomes exposed, water and food have easy access to the sensitive nerve of the teeth, which results in sensitivity.
Sensitive teeth can be managed by using gels, toothpaste and dental procedures that can handle it. It is, however, advisable that you report a sensitivity of teeth to your dentist so that the actual cause can be diagnosed.